About Wire Size & Conductor Ampacity Calculator
Calculate the minimum required American Wire Gauge (AWG) conductor size for copper (THHN/THWN-2) and aluminum (XHHW-2) cables based on continuous load amperage, 75°C terminal temperature ratings, and recommended EMT conduit trade sizes.
Key Capabilities & Features
- Accurate NEC Table 310.16 ampacity benchmarks at 75°C standard termination ratings
- Side-by-side Copper vs Aluminum wire gauge recommendations (14 AWG to 4/0)
- Incorporates 125% continuous duty safety multiplier
- Provides minimum EMT metallic conduit trade size (1/2" up to 2")
- Displays exact ampacity ratings for both conductor materials
How to Use Wire Size & Conductor Ampacity Calculator
Input Circuit Amperage
Set your continuous or non-continuous device current draw in Amperes.
Specify Duty Cycle
Check continuous duty if the electrical equipment operates for 3 hours or longer.
Review Recommended Gauge
Inspect recommended AWG wire gauges and required conduit trade sizes.
Privacy & In-Browser Execution Guarantee
Client-side processing guarantees zero telemetry of facility electrical schematics.
Frequently Asked Questions
Why is aluminum wire typically one or two sizes larger than copper?
Aluminum has approximately 61% the electrical conductivity of copper. To safely carry the same amperage without overheating, an aluminum conductor must have a larger cross-sectional area (circular mils).
What temperature rating should I use for residential breaker terminals?
Most modern circuit breakers and distribution lugs are rated for 75°C. Conductor sizing should be selected from the 75°C column of NEC Table 310.16 even when using 90°C THHN wire.