HVAC CFM Calculator

Calculate HVAC airflow from room size, air changes, system capacity, duct velocity, sensible output, or known airflow.

Calculator is for informational purposes only. Terms and Conditions

Room Airflow from Air Changes
\[ CFM=\frac{LWH\cdot ACH}{60} \]
1

Choose the calculation setup

Select the method that matches the HVAC information you already know.

Choose the method based on whether you know room size, cooling capacity, duct velocity, sensible output and temperatures, or existing airflow.
Changing the preset converts entered values so their physical quantities remain unchanged.
A selected space type inserts an editable planning ACH value. It is not a code-required outdoor-air rate.
Example values are prefilled. Replace them with your room dimensions and intended air-change rate.
2

Enter the known values

Only inputs required by the active method are displayed and enabled.

Enter the inside length of the conditioned room or space.
Enter the inside width of the conditioned room or space.
Use the average clear ceiling height for a sloped or irregular room.
This editable planning value represents total room air changes, not automatically code-required outdoor ventilation.
Advanced Options
3

Airflow Visual

The diagram updates with the active method, inputs, and calculated result.

HVAC CFM calculation diagram A live technical diagram showing the selected HVAC airflow calculation inputs and result.
4

Solution

Live result, practical checks, warnings, and calculation steps.

Required HVAC Airflow
—
—
Enter the required values to calculate.

Quick checks

  • Quick check—
Show solution steps Review conversions, equations, substitutions, assumptions, and result
  1. Enter valid values to see the complete solution.
5

Source, Standards, References, and Assumptions

Calculation basis, authoritative references, limitations, and verification requirements.

Standard HVAC airflow equations

The active method uses standard airflow, air-change, duct-area, capacity, or sensible-heat relationships and does not independently establish code compliance or installed-system performance.

References
  • Enter valid values to see assumptions and limitations for the selected method.

HVAC CFM Calculator

Calculate HVAC airflow from room size, air changes, system capacity, duct velocity, sensible output, or known airflow.

Calculator is for informational purposes only. Terms and Conditions

Room Airflow from Air Changes
\[ CFM=\frac{LWH\cdot ACH}{60} \]
1

Choose the calculation setup

Select the method that matches the HVAC information you already know.

Choose the method based on whether you know room size, cooling capacity, duct velocity, sensible output and temperatures, or existing airflow.
Changing the preset converts entered values so their physical quantities remain unchanged.
Selecting a space inserts a broad, editable circulation-planning example. It is not a required ACH, outdoor-air rate, exhaust rate, or code-compliance value.
Example values are prefilled. Replace them with measured room dimensions and a defensible project-specific air-change assumption.
2

Enter the known values

Only inputs required by the active method are displayed and enabled.

Enter the inside length of the conditioned room or space.
Enter the inside width of the conditioned room or space.
Use the average clear ceiling height for a sloped or irregular room.
This editable value represents assumed total room air changes. It does not determine room heating or cooling airflow and is not automatically the required outdoor-air or exhaust rate.
Advanced Options
3

Airflow Visual

The diagram updates with the active method, inputs, and calculated result.

HVAC CFM calculation diagram A live technical diagram showing the selected HVAC airflow calculation inputs and result.
4

Solution

Live result, practical checks, warnings, and calculation steps.

Required HVAC Airflow
—
—
Enter the required values to calculate.

Quick checks

  • Quick check —
Show solution steps Review conversions, equations, substitutions, assumptions, and result
  1. Enter valid values to see the complete solution.
5

Source, Standards, References, and Assumptions

Calculation basis, authoritative references, limitations, and verification requirements.

Standard HVAC airflow equations

The active method uses standard airflow, room-volume, air-change, duct-area, capacity, or sensible-heat relationships. Results are simplified estimates and do not independently establish code compliance or installed-system performance.

References
  • Enter valid values to see the active assumptions and limitations.
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