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Wire Size Finder.

Find the thinnest NEC-compliant wire gauge for any voltage and distance. Ideal for electricians and engineering teams.

DC
AC 1-PHASE
AC 3-PHASE
Recommended AWG 10 AWG
Calculated Drop 2.07%
Voltage Loss 2.48V
MEETS LIMIT

What Is a Wire Size Calculator?

A wire size calculator is an essential design tool used to determine the exact minimum AWG needed for an electrical circuit. Choosing the correct wire gauge is one of the most critical steps in electrical design. If a wire is too thin, resistance builds up over the distance, generating heat and starving equipment of voltage. If a wire is too thick, money is wasted on unnecessarily expensive copper.

This wire size calculator works the standard voltage drop formula backwards. Instead of entering a wire gauge and seeing the drop, you enter the maximum acceptable drop percentage, and the tool finds the thinnest wire that still meets that requirement.

How to Use This Wire Size Calculator

  1. Select the system type — DC for batteries, AC Single Phase for household circuits, or AC Three Phase for industrial feeders.
  2. Enter the source voltage from the panel or battery (e.g., 120V, 240V, or 12V).
  3. Type the load current — the highest amperage the circuit will carry.
  4. Choose Copper or Aluminum. Copper is standard for branch circuits; aluminum saves cost on large feeders.
  5. Enter the one-way distance from the breaker or battery to the load.
  6. Select the maximum percentage — 3% for NEC branch circuits, 2% for solar, 5% for feeders.

The calculator instantly scans all standard AWG sizes from thinnest to thickest and recommends the minimum wire gauge that stays within the selected limit.

NEC Wire Gauge Quick Reference

AWGDiameter (in)Ω/1000ft (Cu)Typical Use
140.06413.1415A lighting circuits
120.08081.9820A general outlets
100.10191.2430A appliances, solar PV
80.12850.77840A ranges, AC units
60.16200.49155A sub-panels, sub-feeders
40.20430.30870A feeders
20.25760.19495A heavy feeders
1/00.32490.122125A service entrance
4/00.46000.0608195A main service

Frequently Asked Questions

How to calculate wire size for voltage drop? +
Determine the maximum allowable voltage loss in volts (e.g., 3% of 120V = 3.6V). Then work the formula backwards to find the maximum resistance per 1000ft: R = (Vdrop * 1000) / (Mult * I * L). Find the AWG with resistance at or below that value.
What happens if you use wire that is too small? +
Undersized wire creates excessive resistance, leading to overheating (fire risk), voltage starvation (equipment damage), and nuisance breaker tripping.