240V single-phase circuits serve the most power-hungry residential loads: electric dryers, ranges, HVAC equipment, heat pumps, EV chargers, and sub-panel feeders. Because these circuits carry significant current, voltage drop on longer runs can meaningfully reduce appliance performance and efficiency. A heat pump circuit at 240V losing 5% of voltage is operating at only 228V — within tolerance for most equipment, but worth calculating before selecting wire size. This calculator handles 240V single-phase using the standard formula VD = 2 × K × I × D / CM. Enter your load current, run length, and desired wire size to instantly see the voltage drop percentage.
For a 240V 40A EV charger circuit at 80 ft using 8 AWG copper: VD = 2 × 12.9 × 40 × 80 / 16,510 ≈ 5.0V (2.1%). Within NEC 3% branch circuit guideline.
This is a variant of the full Voltage Drop Calculator — which supports all phases, wire materials, and distances in a single tool.
Try all options in the full Voltage Drop Calculator →