Wire size & DC voltage drop

Choose one size input. AWG offers 4/0, 3/0, 2/0, 1/0 and 1–40; their internal indices start at −3, −2, −1 and 0. Metric mode uses the entered conducting area unchanged. Switching modes preserves both drafts. Calculate explicitly after editing.

AWG geometry uses d = 0.127 × 92^(36−n)/39 mm and A = πd²/4. Metric diameter is √(4A/π): an equal-area solid circle, not insulation or strand-bundle diameter. The continuous inverse index is n = 36 − 39 ln(d/0.127)/ln(92). It is a geometric comparison, not a standard wire selection. The geometric progression is described in NBS Handbook 100 (1966), section 2.2. Formula values are unrounded; historical nominal manufacturing tables use rounded dimensions.

Enter the physical forward and return conductor lengths separately. Both use the same material and area: L = Lforward + Lreturn, R = ρL/A, ΔV = IR, loss = I²R. The percentage is 100ΔV divided by the entered supply. Zero current or zero total length gives zero drop and loss. If ΔV exceeds the supply, the entered current is not an operating solution for a passive load at that supply; the arithmetic is still shown.

At 20 °C, standard annealed copper (100% IACS) uses ρ = 1/58 Ω·mm²/m (NBS Handbook 100 (1966), IEC appendix). EC-H19 aluminium uses 0.028264 Ω·mm²/m, approximately 61% IACS (NBS Handbook 109 (1972), table 1). Other alloys and temperatures differ. This DC model excludes heating feedback, contacts, AC effects and current-carrying ratings; it gives no installation or safe-current approval.

Calculation limits: area 0.001–1000 mm², each length 0–100000 m, current 0–10000 A, supply 0.001–1000000 V. Fractions are accepted. These are arithmetic limits, not safety limits. Small drafts use existing cookie storage; drafts that cannot be encoded or exceed 1,500 encoded characters remain available only until reload, with a visible notice.