Estimate electrical wire size from amps, voltage, distance, wire material, phase type, temperature rating, and allowable voltage drop. This calculator gives a planning estimate for copper or aluminum wire gauge.
Current adjustment:
The calculator starts with the load current and applies a 125% factor when continuous load is selected.
Ampacity estimate:
The calculator compares adjusted current to a simplified wire ampacity table.
Voltage drop estimate:
The calculator checks whether the wire size is likely to stay within the selected voltage drop limit for the distance entered.
A wire size calculator helps estimate the electrical wire gauge needed for a circuit before planning a project.
It can help with branch circuits, feeders, garage circuits, shed wiring estimates, RV circuits, solar wiring estimates, low-voltage runs, lighting circuits, and general electrical planning.
Your result shows estimated wire size, adjusted amps, voltage drop, voltage drop percentage, round-trip distance, estimated watts, circuit type, material, and comparison scenarios.
Start with the load current, adjust for continuous load if needed, then choose a wire size that supports the amps and keeps voltage drop within the desired limit.
For a basic copper branch circuit estimate, 12 AWG is commonly associated with 20 amps, but the final answer depends on local code, insulation, temperature, terminals, distance, and circuit type.
Yes. Longer wire runs can create more voltage drop, so a larger wire size may be needed even if the amp load stays the same.
No. This is a planning estimate. Always verify wire sizing, breaker sizing, conduit fill, derating, terminals, and local code requirements with a qualified electrician.