Wire Size Calculator

Recommend AWG wire gauge based on amperage and distance. Shows maximum ampacity for common wire gauges.

Current Load (A)

One-Way Distance (feet)

System Voltage (V)

Max Voltage Drop (%)

Recommended Wire Size—

Voltage Drop at Recommended Size—

AWG Wire Ampacity Reference (Copper, 60°C)

AWG	Max Amps	Typical Use
14	15A	Light fixtures, 15A circuits
12	20A	Kitchen, bathroom outlets
10	30A	Dryers, A/C units
8	40A	Ranges, large A/C
6	55A	Sub-panels, large appliances
4	70A	Feeder circuits
2	95A	Sub-panels, large feeders
1	110A	Service entrance
1/0	125A	Service entrance
2/0	145A	200A service
3/0	165A	200A service
4/0	195A	Large service entrance

How to Choose Wire Size

Select the smallest AWG where: Ampacity ≥ Load AND Voltage Drop ≤ Max %

Wire sizing considers two factors: the wire must handle the current safely (ampacity) and keep voltage drop within acceptable limits for the distance.

The 80% Rule

For continuous loads (running 3+ hours), the NEC requires circuits be loaded to no more than 80% of the wire/breaker rating. A 20A circuit should carry no more than 16A continuously.

Example:
20A load, 75 ft distance, 120V, 3% max drop:
14 AWG: drop = 7.57V (6.3%) ❌
12 AWG: drop = 4.76V (4.0%) ❌
10 AWG: drop = 3.00V (2.5%) ✓
Recommendation: 10 AWG

FAQ

What is AWG?

American Wire Gauge (AWG) is a standardized wire sizing system. Lower numbers indicate larger (thicker) wire with more current-carrying capacity and less resistance.

Should I always use the minimum recommended size?

It's good practice to go one size larger than minimum for future capacity and to account for temperature derating, conduit fill, or bundled wires.

Last updated: 2026-08-08