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Wire Gauge (AWG) Calculator

Work out wire gauge (awg) instantly with clear inputs, formula shown and shareable results.

About Wire Gauge (AWG) Calculator

AWG is a logarithmic scale: area doubles about every three gauge numbers, so 12 AWG is roughly 3.3 mm2. Voltage drop uses the loop length (out and back) times resistivity over area, and on low-voltage DC systems the 3% drop limit usually decides the gauge long before ampacity does.

Formula

AWG and drop

area(mm2) = 0.012668 x 92^((36 - AWG)/19.5) x 0.5067; Vdrop = I x 2 x rho x L / A

Worked example

With the default values below, Wire Gauge (AWG) Calculator returns Voltage drop of 10.2589. Change any input above and every figure here is recalculated in your browser.

Inputs used

AWG size
12 AWG
One-way run length
25 m
Current
20 A
System voltage
12 V

Results

Voltage drop
10.2589 V
Drop as percentage
85.491% %
Conductor area
1.68 mm²
Loop resistance
0.51294 Ω

Step by step

  1. 1Values used
  2. 2AWG and drop
  3. 3Voltage drop= 10.2589 V
  4. 4Drop as percentage= 85.491 %
  5. 5Conductor area= 1.68 mm²
  6. 6Loop resistance= 0.51294 Ω

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why use loop length?

Current flows out along one conductor and back along the other, so both contribute resistance. Using one-way length halves the calculated drop incorrectly.

What drop is acceptable?

3% is the usual target for a final circuit and 5% overall including the feeder. On 12 V systems that is only 0.36 V, which is why cables get thick quickly.

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