Work out wire gauge (awg) instantly with clear inputs, formula shown and shareable results.
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.
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
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.
Current flows out along one conductor and back along the other, so both contribute resistance. Using one-way length halves the calculated drop incorrectly.
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.