Science
Voltage Drop Calculator
Wire voltage drop from resistivity, length, current, and AWG cross-section — with a % check against 120 V and 230 V.
Inputs
Voltage Drop Calculator
Result
Voltage drop
3.118 V
- % of 120 V
- 2.60%
- % of 230 V
- 1.36%
- Recommendation
- Within 3% at 120 V.
How it's calculated
Vdrop = 2 × ρ × L × I / A (round-trip length; A in m², ρ in Ω·m)
Common questions
Why multiply by 2?
The current flows out on one conductor and back on the other, so the total path length is 2 × the one-way distance from source to load.
What's an acceptable voltage drop?
NEC guidance suggests keeping voltage drop under 3% on branch circuits and 5% total (branch + feeder). Larger drops waste energy and stress equipment.
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