Wind Load Calculator
Calculate preliminary ASCE 7-22 directional MWFRS pressure from project coefficients, or estimate basic aerodynamic wind force on an object.
Preliminary engineering calculator only; it does not determine your site wind speed, directional-procedure Cp, Components & Cladding zones, local amendments, tornado loads, or code compliance. Terms and Conditions
Building mode calculates qz at the surface height and qh at mean roof height, then checks both internal-pressure signs using a project-specific directional-procedure Cp.
Choose the wind-load method
Select a preliminary ASCE 7-22 directional MWFRS pressure check or a basic aerodynamic object-force estimate.
Enter the wind and surface values
Required design values remain visible; project-specific factors are grouped under Advanced Options.
For building mode, obtain the site basic wind speed and applicable directional-procedure MWFRS Cp from the governing ASCE 7-22 procedure; enter both surface height z and mean roof height h.
Result
The governing pressure or force is shown first, with both internal-pressure cases and force checks where applicable.
Result details
- Check—
Show calculation stepsReview coefficients, substitutions, pressure cases, conversions, and limitations
- Enter valid values to see the complete calculation.
Pressure / Force Comparison
Compare the calculated pressure cases or the basic object dynamic pressure and effective wind pressure.
- Enter valid values to populate the comparison.
Method, Sources, and Assumptions
Calculation basis, verified references, active assumptions, limitations, and final verification requirements.
Building mode uses the ASCE 7-22 velocity-pressure relationship and revised exposure coefficient, evaluates qz and qh separately, and then checks both internal-pressure signs. It requires a project-specific directional-procedure Cp.
- Enter valid values to see the active assumptions and limitations.
Wind Load Calculator Guide
The Wind Load Calculator above has two distinct uses. In building mode, it calculates an ASCE 7-22 Chapter 27 directional-procedure surface pressure from the wind speed, exposure, enclosure, pressure reference height, mean roof height, loaded area, and a project-specific external pressure coefficient. In basic object mode, it estimates aerodynamic force from wind speed, projected area, air density, and drag coefficient.
The building result is a single-surface pressure check, not a complete wind design for an entire building. It does not select the site wind speed, generate Chapter 27 pressure coefficients, calculate Chapter 28 envelope coefficients, create Components & Cladding pressure zones, or check structural capacity. Use the result to verify a specific pressure case, then continue with the applicable code procedure and load path.
- Building output
- Calculated signed net surface pressure plus both internal-pressure cases and resultant force on the entered area.
- Object output
- Estimated aerodynamic wind force from \(F=\tfrac12\rho V^2C_dA\).
- Primary limitation
- The calculator requires project-specific code inputs such as basic wind speed and Chapter 27 \(C_p\); it does not determine them automatically.
Wind speed is not wind pressure
Wind speed is a velocity, usually reported in mph or m/s. Wind pressure is force per unit area, commonly psf, Pa, or kPa. Wind force is the pressure integrated over an area and is commonly reported in lbf, kip, N, or kN.
How to Use the Wind Load Calculator
Use the calculation mode that matches the engineering question. The two modes use different equations and should not be treated as interchangeable.
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Choose the calculation method
Select ASCE 7-22 Chapter 27 directional pressure for a building MWFRS surface-pressure check using a known \(C_p\). Select Basic aerodynamic object force for a simplified drag-force estimate on a generic object.
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Enter the wind and area data
Building mode requires the project basic wind speed, loaded area, mean roof height, and the pressure height when \(q_z\) is used. Object mode requires incident wind speed and projected frontal area.
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Set the building-specific controls
For Chapter 27 mode, choose Exposure B, C, or D; select the enclosure classification; select whether the external term uses \(q_z\) or \(q_h\); and enter the applicable Chapter 27 directional-procedure \(C_p\). For a partially enclosed building, the positive internal-pressure reference can use \(q_h\) or \(q_i\) evaluated at the highest opening when that option applies.
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Verify the advanced factors
The calculator starts building mode with \(K_{zt}=1.00\), \(K_d=0.85\), \(K_e=1.00\), and \(G=0.85\). These are visible starting assumptions, not universal project values. Confirm each factor before using the result for design.
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Read the sign and both internal-pressure cases
The primary building result reports the pressure case with the larger absolute magnitude. A positive result acts toward the exterior surface under the calculator sign convention; a negative result represents suction acting away from the exterior surface.
Do not guess the site basic wind speed
For ASCE design work, obtain the wind hazard for the project location, risk category, adopted standard, and jurisdiction. ASCE provides the ASCE 7 Hazard Tool, and local code amendments can change the value used for design.
Basic Wind Speed and Risk Category
The most important input to get right is the project basic wind speed. Do not substitute a weather-app gust, sustained hurricane wind, or a generic regional value.
For ASCE 7-22 building calculations, \(V\) is a code-defined basic wind speed associated with the project location and the applicable risk category. The mapped value is based on a 3-second gust reference condition, and the correct value should come from the adopted ASCE hazard data or the authority having jurisdiction.
What risk category changes
Risk Category reflects the consequences of structural failure. Ordinary buildings are commonly associated with Risk Category II, while essential facilities and other higher-consequence occupancies may require Risk Category III or IV. The assigned category affects the wind hazard used for design, so it should be determined from the applicable building-code occupancy provisions before selecting \(V\).
Best input workflow
Determine the project’s risk category first, then obtain the corresponding wind speed for the project coordinates from the ASCE 7 Hazard Tool or the locally adopted code source. Enter that value into the calculator rather than selecting a convenient or familiar wind speed.
Why the calculator does not choose \(V\) automatically
The required wind speed depends on site location, risk category, adopted standard edition, and potentially local amendments. Because those inputs are project-specific, the calculator leaves \(V\) as a user-entered design value instead of guessing it.
Wind Load Formulas and ASCE 7-22 Method
There is no single universal “wind load formula.” The governing relationship depends on whether you are estimating aerodynamic drag on an object or calculating code-based building pressure.
ASCE 7-22 velocity pressure
In U.S. customary units, \(V\) is in mph and \(q_z\) is in psf. In ASCE 7-22, the directionality factor \(K_d\) is not inside the velocity-pressure equation; it is applied later in the Chapter 27 pressure equation.
Chapter 27 directional surface pressure
The external reference pressure \(q\) is \(q_z\) or \(q_h\) as required for the surface. The internal reference \(q_i\) follows the applicable enclosure and Chapter 27 provisions. The calculator checks both signs of \(GC_{pi}\).
ASCE 7-22 exposure coefficient
The calculator applies the ASCE 7-22 form within the applicable height range, uses the 15-ft minimum evaluation height, and caps \(K_z\) at 2.41 above the exposure gradient height within the calculator’s supported range.
Basic aerodynamic object force
This is a drag-force estimate based on air density \(\rho\), wind speed \(V\), drag or force coefficient \(C_d\), and projected area \(A\). It is not a substitute for the applicable ASCE procedure for buildings, signs, rooftop equipment, solar arrays, poles, towers, or other code-regulated structures.
What changed in ASCE 7-22?
ASCE 7-22 revised the wind procedures, including the exposure-coefficient formulation and the placement of the directionality factor. The current calculator therefore uses the 7-22 \(K_z\) relationship and applies \(K_d\) in the pressure expression instead of embedding it inside \(q_z\) or \(q_h\). ASCE describes revised Directional and Envelope procedures among the significant 7-22 wind changes. ASCE: Significant Changes to the Wind Load Provisions of ASCE 7-22
ASCE 7-16 vs ASCE 7-22: changes that affect this calculator
| Item | ASCE 7-16 approach | ASCE 7-22 approach used here |
|---|---|---|
| Velocity pressure coefficient form | \(K_z\) used the older exposure formulation and terrain constants. | \(K_z=2.41(z/z_g)^{2/\alpha}\) with revised 7-22 exposure parameters. |
| Directionality factor \(K_d\) | \(K_d\) was included in the velocity-pressure expression. | \(K_d\) is removed from \(q_z\) and \(q_h\) and applied later in the pressure equation. |
| Exposure B parameters | \(lpha=7.0,\ z_g=1200 ext{ ft}\) | \(lpha=7.5,\ z_g=3280 ext{ ft}\) |
| Exposure C parameters | \(lpha=9.5,\ z_g=900 ext{ ft}\) | \(lpha=9.8,\ z_g=2460 ext{ ft}\) |
| Exposure D parameters | \(lpha=11.5,\ z_g=700 ext{ ft}\) | \(lpha=11.5,\ z_g=1935 ext{ ft}\) |
These changes are why older ASCE 7-16 constants should not be copied into an ASCE 7-22 calculation. The calculator and worked example on this page use the 7-22 formulation consistently.
Do not mix coefficient systems
The calculator’s building mode expects a Chapter 27 directional-procedure \(C_p\). Do not substitute a Chapter 28 \(GC_{pf}\) or a Components & Cladding \(GC_p\). Those coefficients belong to different procedures and pressure equations.
What the Wind Load Inputs Mean
The largest source of error in wind-load calculations is often not arithmetic; it is using the wrong project input, coefficient, surface basis, or enclosure classification.
- \(V\)
- Basic wind speed. For ASCE building mode, use the project design wind speed associated with the applicable location, risk category, standard edition, and jurisdiction—not a weather-app gust.
- \(A\)
- Loaded or projected area. Building mode multiplies the calculated surface pressure by the entered area for a simple resultant force. Object mode uses projected frontal area normal to the wind.
- \(z\)
- Pressure height. Used when the external Chapter 27 surface equation requires \(q_z\), such as the height-dependent windward-wall pressure basis.
- \(h\)
- Mean roof height. Used to calculate \(q_h\), including the internal-pressure reference and external pressure for surfaces whose Chapter 27 equation uses \(q_h\). Do not assume ridge height is automatically the correct value; use the mean-roof-height definition that applies to the actual roof geometry.
- \(C_p\)
- External pressure coefficient. A signed Chapter 27 directional-procedure coefficient selected from the applicable ASCE provisions for the surface and building geometry.
- \(GC_{pi}\)
- Internal pressure coefficient. The calculator derives its magnitude from the selected enclosure classification and evaluates both signs.
- \(K_z\)
- Velocity pressure exposure coefficient. Calculated from height and Exposure B, C, or D using the ASCE 7-22 relationship.
- \(K_{zt}\)
- Topographic factor. Accounts for wind speed-up over qualifying hills, ridges, and escarpments. A starting value of 1.00 means no topographic increase has been applied.
- \(K_d\)
- Directionality factor. Applied in the Chapter 27 pressure equation in ASCE 7-22. The calculator starts at 0.85 for building mode and allows project-specific adjustment.
- \(K_e\)
- Ground elevation factor. Accounts for the effect of elevation on air density in the ASCE velocity-pressure calculation.
- \(G\)
- Gust-effect factor. The calculator starts at 0.85, which is appropriate only when the applicable rigid-building provisions allow it.
- \(\rho, C_d\)
- Object-mode inputs. Air density and drag/force coefficient control the simplified aerodynamic-force estimate and are not used by the Chapter 27 building mode.
Enclosed, partially enclosed, and partially open
ASCE Table 26.13-1 gives \(GC_{pi}=\pm0.18\) for enclosed and partially open buildings and \(GC_{pi}=\pm0.55\) for partially enclosed buildings. The classification depends on the size and distribution of openings, not simply whether the building has doors or windows. ASCE Table 26.13-1 lookup
Open buildings are intentionally not included in this calculator’s Chapter 27 building mode because open free roofs use a different net-pressure-coefficient procedure. That is why “Open” is not an enclosure option in the corrected calculator.
Why the partially enclosed mode has an opening-height option
For positive internal pressure in a partially enclosed building, the calculator can use \(q_h\) or \(q_i\) evaluated at the highest relevant opening, while the negative internal-pressure case uses \(q_h\). The opening-height option exists so the internal pressure reference can reflect that Chapter 27 condition when the project requires it.
ASCE 7-22 Wind Load Example
This example reproduces the corrected calculator’s Chapter 27 equation path. The values are illustrative only; they are not site-specific design inputs.
1. Exposure coefficient
For Exposure C, the ASCE 7-22 terrain parameters used by the calculator are \(\alpha=9.8\) and \(z_g=2460\text{ ft}\).
2. Velocity pressure
Because \(z=h=30\text{ ft}\), \(q_z=q_h\) in this example. \(K_d\) is not included in this ASCE 7-22 velocity-pressure step.
3. External pressure term
4. Check both internal-pressure signs
Calculated result
The larger absolute pressure is \(+24.27\text{ psf}\). On a 200 ft² loaded area, the simple resultant is approximately \(4{,}853\text{ lbf}\), or \(4.85\text{ kip}\).
Independent check
The internal-pressure contribution is \(33.1954\times0.85\times0.18=5.0789\text{ psf}\). Adding and subtracting 5.0789 psf from the 19.187 psf external term reproduces 24.266 psf and 14.108 psf. Multiplying \(24.266\text{ psf}\times200\text{ ft}^2\) reproduces the 4,853 lbf resultant.
How to Interpret Wind Pressure Results
The numerical answer is only useful if the sign, pressure basis, coefficient source, and loaded area are interpreted correctly.
Positive pressure
A positive result acts toward the exterior surface under the calculator’s sign convention. A windward wall is a common example of positive external pressure.
Negative pressure
A negative result is suction acting away from the surface. On a roof, negative pressure commonly represents uplift; on walls, it can pull cladding outward.
Pressure versus force
Pressure is load per unit area. The calculator’s resultant force is simply \(F=pA\) for the entered area; it is not automatically a building base shear or overturning load.
\(q_z\) versus \(q_h\)
\(q_z\) is velocity pressure evaluated at a particular height \(z\). \(q_h\) is the same type of quantity evaluated at mean roof height \(h\). Chapter 27 uses the appropriate pressure basis for each surface; the calculator exposes this choice because using \(q_z\) where \(q_h\) is required, or vice versa, changes the pressure.
MWFRS versus Components & Cladding
Main Wind Force Resisting System
MWFRS refers to the primary structural system that carries wind through frames, bracing, shear walls, diaphragms, collectors, connections, and foundations. The calculator’s Chapter 27 mode is a single-surface MWFRS pressure check using a user-supplied \(C_p\).
Components & Cladding
C&C covers building-envelope elements and their connections, such as roof coverings, wall panels, windows, doors, siding, and local roof/wall zones. ASCE 7-22 includes separate C&C coefficients and zone provisions, so a Chapter 27 \(C_p\) should not be used as a C&C \(GC_p\).
Why edges and corners can govern
Local flow separation and vortices can create stronger suction near roof edges, roof corners, wall corners, and other discontinuities than in broad field areas. That is one reason C&C design uses local pressure zones rather than a single uniform building pressure. ASCE identifies revised roof C&C coefficients and zones among the ASCE 7-22 wind changes. ASCE: Changes to Wind Loads for Components and Cladding Using ASCE 7-22
Fast sanity check: wind pressure scales approximately with speed squared
Holding the other factors and coefficients constant, the velocity-pressure term is proportional to \(V^2\). Increasing wind speed by 10% multiplies that term by \(1.10^2=1.21\), or about 21%. A 20% wind-speed increase produces about 44% more velocity pressure before other changes are considered.
Wind Speed, Exposure, and Pressure Reference
These reference values help explain the calculator inputs. They are not a substitute for selecting the project-specific hazard, exposure, coefficient, and code procedure.
ASCE 7-22 exposure parameters used by the calculator
| Exposure | \(\alpha\) | \(z_g\) (ft) | Practical terrain description |
|---|---|---|---|
| B | 7.5 | 3,280 | Urban, suburban, wooded, or similarly rough terrain with numerous closely spaced obstructions. |
| C | 9.8 | 2,460 | Open terrain with scattered obstructions, including open country and grasslands. |
| D | 11.5 | 1,935 | Flat unobstructed terrain and water-surface exposure where the ASCE fetch criteria are satisfied. |
The revised ASCE 7-22 \(K_z\) formulation and terrain coefficients are documented in current ASCE 7-22 implementation guidance. Trimble: ASCE 7-22 updates. FEMA also explains the practical distinction between Exposure B and C in its wind-retrofit guidance. FEMA wind exposure guidance.
Wind speed to basic pressure relationship
The table below shows only the reference relationship \(0.00256V^2\). It deliberately excludes \(K_z\), \(K_{zt}\), \(K_e\), \(K_d\), \(G\), \(C_p\), and internal pressure, so it must not be treated as final ASCE design pressure.
| Wind speed (mph) | Reference pressure (psf) |
|---|---|
| 50 | 6.4 |
| 75 | 14.4 |
| 100 | 25.6 |
| 115 | 33.9 |
| 130 | 43.3 |
| 150 | 57.6 |
Do not choose Exposure B just because the project is in a neighborhood
Exposure classification depends on the upwind terrain and the standard’s exposure rules, not only the immediate lot. A nearby open field, shoreline, or long unobstructed fetch can change the applicable exposure because the required upwind distance and terrain condition must satisfy the ASCE exposure criteria.
Common Wind Load Calculation Mistakes
Wind calculations are especially vulnerable to “correct arithmetic, wrong input” errors. Check these items before trusting a polished numerical result.
- Using weather data as the code wind speed. The ASCE basic wind speed is a design hazard value tied to location and risk category, not an ordinary forecast or observed sustained wind.
- Mixing ASCE editions. ASCE 7-22 revised the \(K_z\) relationship and relocated \(K_d\). Do not combine a 7-22 pressure equation with older exposure constants.
- Using the wrong pressure basis. Chapter 27 does not use \(q_z\) for every surface. Confirm whether the external term requires \(q_z\) or \(q_h\).
- Confusing \(C_p\), \(GC_{pf}\), and \(GC_p\). Chapter 27, Chapter 28, and Components & Cladding use different coefficient systems.
- Checking only one internal-pressure sign. The critical pressure can switch depending on the external coefficient and surface.
- Misclassifying a building as partially enclosed. Enclosure is determined by opening-area criteria, not by a general impression that the building has “large openings.”
- Assuming \(K_{zt}=1.00\) proves topography is irrelevant. It only means no topographic speed-up has been applied in the calculation.
- Using ridge height as mean roof height without checking the definition. The correct \(h\) depends on the roof geometry and the applicable ASCE definition.
- Multiplying by the wrong area. The calculator’s force result is pressure times the area you entered; the correct tributary or projected area still has to be selected by the user.
- Treating a negative result as zero load. Negative pressure is suction and can govern roof uplift, cladding, anchors, and connections.
- Using the basic drag equation for code building design. \(F=\tfrac12\rho V^2C_dA\) is useful for aerodynamic estimates but does not replace the ASCE building procedures.
- Stopping at pressure. Final design still needs load cases, minimum-load checks, load combinations, structural analysis, connection design, and a continuous load path to the foundation.
Limits of This Wind Load Calculator
Wind loading is a Tier 3 structural-design problem. The calculator is useful for transparent preliminary checks, but a valid number from the tool is not the same as a complete code-compliant design.
It does not select \(V\)
Use the applicable ASCE hazard data and jurisdictional requirements to establish the project basic wind speed and risk category.
It does not select \(C_p\)
The calculator intentionally requires the Chapter 27 directional-procedure external coefficient because surface, building proportions, roof geometry, and wind direction affect the value.
It is not a C&C zone generator
Roof and wall edge/corner zones, effective wind area, and Chapter 30 \(GC_p\) values require the separate Components & Cladding procedure.
It does not handle open free roofs
Open free-roof structures use a different Chapter 27 net-pressure-coefficient procedure, so the building mode excludes the “Open” enclosure classification.
It does not check structural resistance
Pressure must still be converted into member, diaphragm, connection, anchor, and foundation demands and compared with the applicable strength and serviceability limits.
It does not perform tornado design
ASCE 7-22 added Chapter 32 tornado provisions for applicable structures. Tornado hazard, pressure equations, coefficients, load combinations, and debris requirements are distinct from conventional wind design.
ASCE 7-22 is not static
ASCE publishes supplements and errata for the standard. Before final design, check the edition adopted by the authority having jurisdiction and the applicable ASCE 7-22 supplements and errata. ASCE 7 supplements and errata.
Conventional wind load is not a tornado-load check
FEMA and NIST published a dedicated guide for the new ASCE 7-22 tornado requirements because tornado design differs from conventional wind design in hazard, velocity profile, directionality, enclosure, pressure coefficients, load combinations, and other provisions. FEMA/NIST ASCE 7-22 Tornado Load Design Guide.
Sources and Calculation Basis
The calculator and this guide use ASCE 7-22 as the reference basis for the building-mode methodology, with supporting public guidance used to explain changes, exposure, and tornado scope.
- ASCE/SEI 7-22 — Minimum Design Loads and Associated Criteria for Buildings and Other Structures. ASCE’s standard page also lists the available 7-22 supplements and errata.
- ASCE — Significant Changes to the Wind Load Provisions of ASCE 7-22, Part 2. Covers changes to the Directional and Envelope wind procedures.
- ASCE 7-22 standard and supporting materials. Use the current standard provisions for enclosure classification, internal pressure coefficients, Chapter 27 coefficients, and project-specific wind design requirements.
- Trimble Structural Designer — ASCE 7-22 updates. Documents the revised \(K_z\) equation, exposure parameters, and the relocation of \(K_d\) from velocity pressure to later pressure calculations.
- FEMA — Hurricane Wind Retrofit Technical Review Job Aid. Provides practical descriptions of wind Exposure B and C and emphasizes using the code-required exposure for actual design.
- FEMA/NIST — Design Guide for New Tornado Load Requirements in ASCE 7-22. Explains when separate Chapter 32 tornado-load design may be required.
How the worked example was checked
The example was recomputed independently from the ASCE 7-22 \(K_z\), velocity-pressure, external-pressure, and internal-pressure relationships. The two \(GC_{pi}\) cases were then checked by adding and subtracting the independently calculated internal-pressure contribution from the external term, and the reported force was checked with \(F=pA\).
Wind Load Calculator FAQ
How do you calculate wind load?
For a basic object-force estimate, use \(F=\tfrac12\rho V^2C_dA\). Building design under ASCE 7-22 is more involved: determine the project wind hazard and exposure, calculate velocity pressure, apply the applicable directionality, gust, external, and internal pressure terms, and then evaluate the required surfaces and load cases.
What is the wind pressure at 100 mph?
The simple reference relationship \(0.00256V^2\) gives \(25.6\text{ psf}\) at 100 mph. That is not automatically the final ASCE building pressure because exposure, height, topography, elevation, directionality, gust effect, external coefficients, and internal pressure can change the design value.
What is the difference between \(q_z\) and \(q_h\)?
\(q_z\) is velocity pressure at a specific height \(z\); \(q_h\) is velocity pressure at mean roof height \(h\). The correct external pressure basis depends on the Chapter 27 surface equation, while \(q_h\) is also important for internal pressure.
What does negative wind pressure mean?
Negative wind pressure represents suction acting away from the exterior surface under the calculator sign convention. On a roof this commonly corresponds to uplift; on a wall it can pull cladding outward.
What is Exposure B, C, or D?
Exposure categories describe upwind terrain roughness. Exposure B represents built-up or wooded rough terrain; Exposure C represents more open terrain with scattered obstructions; Exposure D represents qualifying flat unobstructed terrain and water exposure. The exact classification must follow the ASCE exposure criteria and upwind fetch requirements.
What is the difference between MWFRS and Components & Cladding?
MWFRS is the primary structural system that transfers wind through the building. Components & Cladding are local envelope elements and connections such as roof coverings, siding, panels, doors, and windows. They use different ASCE coefficient and zoning procedures.
Why must both signs of \(GC_{pi}\) be checked?
Internal pressure can act toward or away from the interior surfaces. Either sign can make the net external-surface pressure more severe depending on \(C_p\) and the pressure reference, so the calculator evaluates both cases and reports the larger absolute pressure.
Why does ASCE 7-22 apply \(K_d\) outside the velocity-pressure equation?
ASCE 7-22 relocated the directionality factor from the \(q_z\) and \(q_h\) expressions into the wind-pressure equations in Chapters 27 through 30. This is why the corrected calculator computes velocity pressure without \(K_d\) and applies \(K_d\) in the Chapter 27 surface-pressure calculation.
Can I use this calculator for roof uplift or cladding design?
You can use Chapter 27 mode to check a specific MWFRS surface-pressure case when you already have the correct Chapter 27 \(C_p\). Do not use it as a Chapter 30 Components & Cladding zone calculator. Roof coverings, edge and corner zones, effective wind area, fasteners, doors, windows, and cladding require the applicable C&C procedure.
Does the calculator prove code compliance?
No. It performs a transparent pressure or aerodynamic-force calculation from the entered inputs. Final design still depends on the adopted code, current ASCE provisions and supplements, hazard data, geometry, minimum loads, load combinations, structural analysis, material design, connection design, and the authority having jurisdiction.