DC Voltage Drop
Calculate voltage drop in a DC circuit (two-conductor).
Inputs
Results
This uses DC resistance only (no reactance). Fine for rough branch circuit checks.
You're at 6.5% drop. A lot of folks cap feeders at 5%. Consider bigger wire or a shorter run.
Voltage Drop
3.10 V
(6.46%)
| Voltage Drop | 3.10 V |
|---|---|
| Drop % | 6.46% % |
| Voltage at Load | 44.90 V |
· The 3% and 5% numbers are common rules of thumb, not code.
How It Works
DC voltage drop (two wires): Voltage drop = 2 x I x R Same idea as single-phase AC: two conductors, so 2 x I x R. We use DC resistance only (no reactance).
Example
10 AWG copper, 1.24 ohms per 1000 ft, 50 ft, 25 A: voltage drop = 2 x 25 x (1.24/1000 x 50) = 3.1 V, or 6.5%.
Frequently Asked Questions
Is DC voltage drop the same formula as single-phase AC?
For two conductors, yes. Voltage drop = 2 x I x R for both. This tool uses DC resistance only; real AC circuits have some reactance we are not including here.
These numbers are for reference only. We are not liable for any decisions you make or how you use these results in the real world. Check the current NEC and your local codes, and have a licensed electrician sign off before you install or buy. Full disclaimer