Electronics & Engineering

AWG Wire Gauge Calculator

Convert an American Wire Gauge number to millimetres and ohms per kilometre.

By TheCalcTools Updated Formula checked and tested

Your numbers

Your results

Diameter (mm)
Diameter (mm)
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Cross-section (mm²)
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Resistance, copper at 20 °C (Ω/km)
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AWG Wire Gauge Calculator by TheCalcTools

How the AWG Wire Gauge Calculator works

Enter the AWG gauge number.

Each gauge step changes the diameter by a factor of 92^(1/39), about 1.123, and each three steps halve the area.

Resistance uses the resistivity of annealed copper at 20 °C.

The formula

d (mm) = 0.127 × 92^((36 − n) ÷ 39)R = ρ × L ÷ A, with ρ = 1.7241 × 10⁻⁸ Ω·m

Worked example

Using the default values shown in the calculator:

AWG gauge10
  1. d = 0.127 × 92^(26 ÷ 39) = 2.588 mm.
  2. Area = π × d² ÷ 4 = 5.261 mm².
  3. Resistance = 3.277 Ω per km.

Result:

Diameter (mm)2.588
Cross-section (mm²)5.261
Resistance, copper at 20 °C (Ω/km)3.277

Frequently asked questions

Why do smaller AWG numbers mean thicker wire?

The gauge counts the number of drawing steps. More drawing makes thinner wire, so a higher number is thinner.

How much current can a wire carry?

It depends on insulation, bundling and temperature. Follow the electrical code or datasheet rather than this calculator.

Sources and further reading

Voltage Drop CalculatorCheck whether a cable run is too long for the current it carries Ohm's Law CalculatorPick the two values you know and get the other two Wire Resistance CalculatorHow much resistance does a length of wire add to your circuit?

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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.