AWG 20 voltage drop calculator
Voltage drop is current times the resistance of the round trip. For AWG 20 the resistance comes straight from the gauge definition and the conductor resistivity.
A
V
Voltage drop
17.377%
- Voltage lost in the cable
- 39.9676 V
- Voltage at the load
- 190.032 V
- Power lost as heat
- 799.35
- Resistance per metre
- 0.033 306 3 ohm/m
- Conductor area
- 0.517 619 mm2
- Longest run within 3% drop
- 5.18
Show the working
- Current = 20
- One-way run length = 30
- Supply voltage = 230
- System = 2
- Conductor = 1.724e-8
- Conductor temperature = 20
- diameter_mm = 0.127 * 92^((36 - (20)) / 39) = 0.811 821
- Conductor area = pi * 0.811 821^2 / 4 = 0.517 619
- Resistance per metre = 1.724e-8 / (0.517 619 * 1e-6) * (1 + 0.00393 * (20 - 20)) = 0.033 306 3
- Voltage lost in the cable = 2 * 20 * 0.033 306 3 * 30 = 39.9676
- Voltage drop = 39.9676 / 230 * 100 = 17.3772
- Voltage at the load = 230 - 39.9676 = 190.032
- Power lost as heat = 39.9676 * 20 = 799.352
- Longest run within 3% drop = 0.033 306 3 > 0 && 20 > 0 ? 230 * 0.03 / (2 * 20 * 0.033 306 3) : 0 = 5.179 19
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
Scenarios & local history
Compare a saved scenario
Recent calculations
The formula
- single phase or DC: drop = 2 x I x R per metre x one-way length
- three phase: drop = sqrt(3) x I x R per metre x one-way length
- R per metre = rho / area, corrected for temperature
The factor of two on a single-phase run is because the current goes out and comes back. A three-phase drop uses sqrt(3) because the return currents partly cancel.
This is resistive drop only. On long AC runs at high current, cable reactance adds to it.
Warm conductors have more resistance: at 70 degrees Celsius copper is about 20% more resistive than at 20.