What Size Wire for a 30 Amp Circuit Breaker? (NEC Table 310.16)

Complete Copper vs. Aluminum AWG wire size, continuous load limit (24A max), ground wire gauge, and conduit sizing for 30A circuits (Electric clothes dryers, 30A RV shore power & electric water heaters).

Direct NEC Table 310.16 Answer for 30 Amps

10 AWG

Minimum Copper Wire (75°C)

THHN / THWN-2 / XHHW in Conduit

8 AWG

Minimum Aluminum Wire (75°C)

SER / XHHW-2 Feeder Cable

24 Amps

Max Continuous Load (80% Rule)

For loads running 3+ hours (EVs, lighting)

1/2" EMT

Recommended Conduit Size

Fits 3x 10 AWG + Ground under 40% fill

Common Applications for a 30A Circuit

Electric clothes dryers, 30A RV shore power & electric water heaters. Remember that under the NEC 125% continuous-load rule (NEC 210.19 & 210.20), a standard 30A breaker can only supply up to 24A of continuous load (any load that runs for 3 hours or more without stopping, such as an EV charger or commercial lighting).

When to Upsize for Voltage Drop (Over 100 Feet)

If your one-way wire run exceeds 100 feet at 240V (or 50 feet at 120V), step up one wire gauge from 10 AWG to keep total line voltage drop under the NEC 3% branch-circuit recommendation. Use our Voltage Drop Calculator to check your exact footage.

2. NEC Wire Size & Ampacity Calculator (Table 310.16)

Load Current (Amps)

Conductor Metal

Terminal Temp Rating

Conductors in Raceway

Continuous Load (runs 3+ hours continuously — apply NEC 125% rule)

What Size Wire for a 30 Amp Circuit Breaker? (NEC Table 310.16)

Direct NEC Table 310.16 Answer for 30 Amps

Common Applications for a 30A Circuit

When to Upsize for Voltage Drop (Over 100 Feet)

2. NEC Wire Size & Ampacity Calculator (Table 310.16)

Recommended Wire, Breakers & Termination Tools