Interactive Electrical Engineering Reference

Wire Ampacity Chart

Look up copper and aluminum conductor ampacity by wire size, then select up to three rows to compare 60°C, 75°C, and 90°C values.

Base condition: 30°C ambient
Units: amperes
Materials: copper and aluminum
Use: preliminary reference

Find a wire size: filter or search the table, then select up to three rows for the comparison chart below.

Educational ampacity reference based on commonly used NEC Table 310.16 values for not more than three current-carrying conductors in a raceway, cable, or earth at 30°C ambient. Final design remains subject to all applicable code rules and equipment limitations.
Select			Allowable ampacity by conductor temperature rating			Action
Select						Action
	14 AWG	Copper	15 A	20 A	25 A
	12 AWG	Copper	20 A	25 A	30 A
	10 AWG	Copper	30 A	35 A	40 A
	8 AWG	Copper	40 A	50 A	55 A
	6 AWG	Copper	55 A	65 A	75 A
	4 AWG	Copper	70 A	85 A	95 A
	3 AWG	Copper	85 A	100 A	115 A
	2 AWG	Copper	95 A	115 A	130 A
	1 AWG	Copper	110 A	130 A	145 A
	1/0 AWG	Copper	125 A	150 A	170 A
	2/0 AWG	Copper	145 A	175 A	195 A
	3/0 AWG	Copper	165 A	200 A	225 A
	4/0 AWG	Copper	195 A	230 A	260 A
	250 kcmil	Copper	215 A	255 A	290 A
	300 kcmil	Copper	240 A	285 A	320 A
	350 kcmil	Copper	260 A	310 A	350 A
	400 kcmil	Copper	280 A	335 A	380 A
	500 kcmil	Copper	320 A	380 A	430 A
	600 kcmil	Copper	350 A	420 A	475 A
	750 kcmil	Copper	400 A	475 A	535 A
	1000 kcmil	Copper	455 A	545 A	615 A
	12 AWG	Aluminum	15 A	20 A	25 A
	10 AWG	Aluminum	25 A	30 A	35 A
	8 AWG	Aluminum	30 A	40 A	45 A
	6 AWG	Aluminum	40 A	50 A	55 A
	4 AWG	Aluminum	55 A	65 A	75 A
	3 AWG	Aluminum	65 A	75 A	85 A
	2 AWG	Aluminum	75 A	90 A	100 A
	1 AWG	Aluminum	85 A	100 A	115 A
	1/0 AWG	Aluminum	100 A	120 A	135 A
	2/0 AWG	Aluminum	115 A	135 A	150 A
	3/0 AWG	Aluminum	130 A	155 A	175 A
	4/0 AWG	Aluminum	150 A	180 A	205 A
	250 kcmil	Aluminum	170 A	205 A	230 A
	300 kcmil	Aluminum	195 A	230 A	260 A
	350 kcmil	Aluminum	210 A	250 A	280 A
	400 kcmil	Aluminum	225 A	270 A	305 A
	500 kcmil	Aluminum	260 A	310 A	350 A
	600 kcmil	Aluminum	285 A	340 A	385 A
	750 kcmil	Aluminum	320 A	385 A	435 A
	1000 kcmil	Aluminum	375 A	445 A	500 A

Important: These are base reference values, not automatic breaker sizes or final conductor selections. The 90°C column may be useful for correction and adjustment calculations when permitted, but lower terminal, equipment, conductor-protection, or application-specific limits may govern.

More filters and comparison options

Bulk CSV download is intentionally unavailable because NEC/NFPA table content is copyrighted. Use the copy-row action for a limited result summary and consult the official standard for authoritative project use.

Interactive comparison

Ampacity Comparison for Selected Conductors

Select up to three conductors in the table to compare their ampacity.

Optional chart controls

Refine the Comparison Chart

Table checkboxes are the primary selector. These dropdowns provide a faster alternative on small screens.

Changing these dropdowns updates the same selected rows and chart shown above.

Key Takeaways

Do not select the largest number: A 90°C insulation rating does not automatically make the 90°C table value the final allowable ampacity.
Apply both types of derating: Ambient-temperature correction and current-carrying-conductor adjustment address different thermal conditions.
Check the complete circuit: Ampacity, overcurrent protection, continuous load, equipment rules, and voltage drop are related but separate checks.
Confirm the adopted code: The applicable NEC edition and local amendments are determined by the jurisdiction and authority having jurisdiction.

Important Wire Ampacity Limitations

Do not use this chart as installation approval

This page is an educational conductor-ampacity reference. It does not verify the wiring method, equipment listing, terminal markings, conductor insulation, conductor-count exceptions, neutral treatment, rooftop conditions, cable-tray requirements, service-conductor rules, motor rules, HVAC rules, photovoltaic rules, flexible-cord requirements, parallel-conductor design, or local amendments for a specific installation.

Method and interpretation

How to Use the Wire Ampacity Chart

Follow the complete selection path instead of stopping at one table cell.

Identify the correct conductor material and size. Copper and aluminum conductors have different allowable ampacities for the same designation.
Select the applicable conductor temperature rating. The insulation type and code rules determine which temperature column may be used for calculations.
Apply installation-condition factors. Correct for ambient temperature and adjust for the number of current-carrying conductors when required.
Apply the lowest governing limitation. Compare the adjusted result with terminal ratings, equipment limitations, conductor-protection rules, and special application requirements.

Variables, Symbols, and Units

\(I_{\text{base}}\): Base ampacity in amperes from the applicable conductor temperature column.

\(F_{\text{ambient}}\): Ambient-temperature correction factor, expressed as a dimensionless multiplier.

\(F_{\text{conductors}}\): Adjustment factor for the applicable number of current-carrying conductors.

\(I_{\text{adjusted}}\): Calculated ampacity after the selected correction and adjustment factors.

Why the Temperature Columns Differ

The 60°C, 75°C, and 90°C columns represent conductor ampacities associated with different allowable conductor temperature ratings. A conductor may have 90°C-rated insulation while being connected to equipment with lower-rated terminals. In that case, the higher insulation rating can sometimes be used during correction or adjustment calculations, but the final permitted ampacity remains subject to the lower applicable terminal or equipment limitation.

60°C column

Commonly relevant where equipment terminals or conductor-use rules impose a 60°C limitation.

75°C column

Frequently used with equipment and conductors specifically identified for 75°C terminations.

90°C column

Often useful as the starting value for permitted correction and adjustment calculations, but not automatically the final circuit ampacity.

Ambient-Temperature Correction Factors Used by the Tool

The calculator uses temperature bands associated with 60°C, 75°C, and 90°C conductor ratings. It does not interpolate between bands or extrapolate outside the supported range.

Ambient-temperature correction factors applied by the interactive lookup.
Ambient temperature	60°C conductor	75°C conductor	90°C conductor
10°C or less	1.29	1.20	1.15
11–15°C	1.22	1.15	1.12
16–20°C	1.15	1.11	1.08
21–25°C	1.08	1.05	1.04
26–30°C	1.00	1.00	1.00
31–35°C	0.91	0.94	0.96
36–40°C	0.82	0.88	0.91
41–45°C	0.71	0.82	0.87
46–50°C	0.58	0.75	0.82
51–55°C	0.41	0.67	0.76
56–60°C	—	0.58	0.71
61–65°C	—	0.47	0.65
66–70°C	—	0.33	0.58
71–75°C	—	—	0.50
76–80°C	—	—	0.41

Current-Carrying-Conductor Adjustment Used by the Tool

Adjustment factors selected by the entered number of current-carrying conductors.
Current-carrying conductors	Adjustment factor
1–3	100%
4–6	80%
7–9	70%
10–20	50%
21–30	45%
31–40	40%
41 or more	35%

Conductor-count caution

Do not assume every conductor in a raceway or cable is counted the same way. Equipment grounding conductors are not normally current carrying, and neutral-conductor treatment can depend on the circuit. Verify the applicable counting rules for the actual installation.

Worked ampacity examples

Wire Ampacity Calculation Examples

12 AWG Copper With 90°C Insulation and 60°C Terminations

Given: 12 AWG copper, 90°C insulation, 60°C terminations, 30°C ambient, and three current-carrying conductors.

Method: The 90°C base value is 30 A. Both correction factors equal 1.00, but the 60°C reference value is 20 A.

Result: The preliminary governing ampacity is 20 A because the lower termination limitation controls.

Check: Small-conductor overcurrent-protection rules and the actual equipment markings must still be verified.

6 AWG Copper in 40°C Ambient With Six Current-Carrying Conductors

Given: 6 AWG copper, 90°C insulation, 75°C terminations, 40°C ambient, and six current-carrying conductors.

Method: Start with 75 A from the 90°C column, multiply by 0.91 for ambient temperature and 0.80 for conductor count.

Result: Adjusted ampacity is \(75 \times 0.91 \times 0.80 = 54.6\text{ A}\).

Check: The adjusted value is below the 65 A value associated with the 75°C column, so the selected thermal adjustments govern this simplified example.

Engineering decision guide

What to Select, Check, and Avoid

Use this chart when

You need a quick copper or aluminum conductor ampacity lookup.
You want to compare 60°C, 75°C, and 90°C table columns.
You need a preliminary first-size check after basic derating.

Verify separately

Breaker or fuse selection and small-conductor protection rules.
Voltage drop, fault current, short-circuit withstand, and equipment instructions.
Special rules for motors, HVAC, EV charging, PV, services, feeders, welders, cable tray, flexible cords, and parallel conductors.

Common mistakes

Using the 90°C value as the final ampacity without checking terminals.
Confusing conduit fill with current-carrying-conductor adjustment.
Selecting a breaker directly from one ampacity table value.

Copper vs. Aluminum Wire Ampacity

Aluminum conductors generally require a larger conductor designation than copper to provide a comparable ampacity. Material selection also affects conductor size, weight, cost, termination requirements, equipment compatibility, installation practices, and oxidation-control requirements. The ampacity chart is therefore only one part of a material-selection decision.

Ampacity vs. Breaker Size vs. Voltage Drop

Ampacity: The conductor’s allowable current under defined thermal and installation conditions.

Breaker size: The overcurrent-protection rating selected under applicable load, equipment, conductor, and code rules.

Voltage drop: The reduction in voltage caused by conductor impedance over the circuit length.

Design current: The current that the conductor and protective system must serve after applicable load factors are considered.

When This Wire Ampacity Chart Does Not Apply

Another table or calculation method may be required for conductors in free air, flexible cords, service conductors, medium-voltage conductors, cable tray, rooftop raceways, direct sunlight, high-temperature equipment, parallel conductors, motors, generators, transformers, welders, HVAC equipment, electric-vehicle charging systems, photovoltaic systems, storage batteries, or manufacturer-controlled assemblies.

Wire Ampacity Chart Engineering References

NEC conductor ampacity reference · AWG, kcmil and amperes · Dataset version 1.0

The page uses a transformed educational presentation of conductor ampacity concepts and commonly referenced values. The official NFPA publication remains the controlling source for project-specific code work.

NFPA 70, National Electrical CodeSupports conductor ampacity tables, temperature limitations, correction factors, adjustment factors, and related code requirements.
IAEI: The Reorganization of NEC Article 310Supports explanatory context for Article 310 organization and ampacity terminology.
University of Maryland Extension: Working on Solar Wiring and FusingSupports educational discussion of conductor sizing and temperature correction in elevated-temperature installations.

Dataset and Review Details

Edition or revision: 2023 NEC educational basis; verify locally adopted edition
Method: Base ampacity × ambient factor × conductor-count factor, then governing-limit comparison
Scope: Copper and aluminum insulated conductors from common AWG through 1000 kcmil sizes
Known exclusions: Special applications, alternate wiring methods, local amendments, equipment-specific rules, and project approval
Last reviewed: August 1, 2026
Engineering reviewer: Turn2Engineering Editorial Team
Rights status: Limited educational transformation; no full NEC-derived CSV distribution
Dataset version: Wire Ampacity Reference 1.0

Frequently Asked Questions

How many amps can 12-gauge wire carry?

The reference values for 12 AWG copper are 20 A at 60°C, 25 A at 75°C, and 30 A at 90°C, but that does not mean every 12 AWG installation may be used at those currents. Terminal ratings, small-conductor overcurrent-protection rules, wiring method, insulation, ambient temperature, conductor count, equipment rules, and local code determine the final permitted application.

Why does a wire ampacity chart show three amp ratings?

The three values correspond to 60°C, 75°C, and 90°C conductor temperature ratings. The applicable value depends on conductor insulation, terminal ratings, equipment markings, conductor size, and code rules. The highest value is not automatically the allowable circuit ampacity.

Can I use the 90°C ampacity for THHN wire?

A 90°C conductor rating may be used as the starting value for permitted correction and adjustment calculations, but the final ampacity remains limited by applicable terminal ratings, equipment instructions, conductor-protection rules, and other code requirements.

Does wire ampacity decrease in hot locations?

Yes. When ambient temperature exceeds the table’s reference condition, an applicable correction factor can reduce conductor ampacity. Additional adjustments may also be required for multiple current-carrying conductors or special installation conditions.

Is wire ampacity the same as breaker size?

No. Ampacity is a conductor thermal limit under defined conditions. Breaker or fuse selection also depends on load characteristics, continuous operation, equipment requirements, conductor-protection rules, permitted standard ratings, and application-specific NEC provisions.

Wire Ampacity Chart Summary

Use the interactive chart to identify a base conductor ampacity, apply supported ambient-temperature and conductor-count factors, and see which selected limitation governs. The result is most useful as a transparent preliminary check because it shows the calculation path instead of returning one unexplained number.

Complete conductor design requires more than an ampacity table. After confirming the applicable code edition and installation method, check overcurrent protection, voltage drop, equipment instructions, special application rules, fault-current requirements, and local amendments.

Where to Go Next

Complete the cable sizing calculation
Evaluate conductor selection using a broader sizing workflow.
Check voltage drop for the circuit length
Determine whether distance requires a larger conductor than ampacity alone.