AWG 13 voltage drop calculator
Voltage drop is current times the resistance of the round trip. For AWG 13 the resistance comes straight from the gauge definition and the conductor resistivity.
A
V
Voltage drop
3.428%
- Voltage lost in the cable
- 7.8842 V
- Voltage at the load
- 222.116 V
- Power lost as heat
- 157.68
- Resistance per metre
- 0.006 570 18 ohm/m
- Conductor area
- 2.623 98 mm2
- Longest run within 3% drop
- 26.25
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 - (13)) / 39) = 1.827 83
- Conductor area = pi * 1.827 83^2 / 4 = 2.623 98
- Resistance per metre = 1.724e-8 / (2.623 98 * 1e-6) * (1 + 0.00393 * (20 - 20)) = 0.006 570 18
- Voltage lost in the cable = 2 * 20 * 0.006 570 18 * 30 = 7.884 22
- Voltage drop = 7.884 22 / 230 * 100 = 3.427 92
- Voltage at the load = 230 - 7.884 22 = 222.116
- Power lost as heat = 7.884 22 * 20 = 157.684
- Longest run within 3% drop = 0.006 570 18 > 0 && 20 > 0 ? 230 * 0.03 / (2 * 20 * 0.006 570 18) : 0 = 26.255
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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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.