What ampacity table is used?

NEC Table 310.16, 75°C column for copper and aluminum conductors in raceway.

Are neutral conductors counted for bundling?

This tool uses your entered conductor count. Under NEC 310.15(C)(1), neutrals that carry unbalanced current count as current-carrying.

Why 75°C and not 90°C?

Many terminations are limited to 75°C unless equipment is listed for 90°C. We apply 75°C as a conservative default.

Field electrical

Wire Size & Ampacity Calculator

Size conductors using NEC Table 310.16 ampacity with temperature and bundling adjustments.

Licensed electrician working on panel wiring

Load & conditions

Load current (A)

Conductor material

Ambient temperature (°C)

Current-carrying conductors in raceway

Continuous load (125% sizing per NEC 210.19)

How to use this wire size tool

Enter the circuit load current in amperes.
Select copper or aluminum and ambient temperature.
Enter the count of current-carrying conductors in the raceway.
Enable continuous load if the load runs 3+ hours (125% factor).

Disclaimer

Ampacity results do not replace a full NEC load calculation. Termination temperature limits, ambient derating, and overcurrent protection must be coordinated separately.

Sources & references

NEC Table 310.16 — Allowable ampacities

Based on NFPA 70 (NEC) 2023 unless noted. Confirm the edition adopted locally.

Frequently asked questions

What ampacity table is used?: NEC Table 310.16, 75°C column for copper and aluminum conductors in raceway.
Are neutral conductors counted for bundling?: This tool uses your entered conductor count. Under NEC 310.15(C)(1), neutrals that carry unbalanced current count as current-carrying.
Why 75°C and not 90°C?: Many terminations are limited to 75°C unless equipment is listed for 90°C. We apply 75°C as a conservative default.