Voltage Drop Calculator
Calculate voltage drop over a wire run from AWG gauge, length, current, and circuit type, with a 3% warning.
Processed locally in your browser — nothing is uploaded.
Distance from source to load, not the round trip.
Results
- Voltage drop
- 1.588 V
- Drop percentage
- 1.32%
- Voltage at the load
- 118.41 V
Based on 20°C copper resistance (aluminum ≈ 1.64× copper) and resistive load. Conductor temperature and power factor shift real-world results — treat this as guidance, not an electrical-code calculation.
About Voltage Drop Calculator
Pick a wire gauge and material, enter the one-way run length, load current, and source voltage, and see the voltage drop, percentage drop, and what actually arrives at the load. DC and single-phase AC use the round-trip (×2) conductor length; three-phase uses the √3 factor.
Resistance values are the standard 20°C annealed-copper table (aluminum ≈ 1.64× copper). Drops above 3% are flagged, matching the common design recommendation for branch circuits.
Common uses
- Check whether a long extension run will brown out a power tool
- Size 12 V wiring in a van, boat, or solar build where drop hurts most
- Verify a feeder run stays inside the 3% guideline
Example
Input
12 AWG copper · 50 ft one-way · 10 A · 120 V single-phase
Output
1.59 V drop (1.32%) · 118.4 V at the load
Limitations
- Conductor temperature, power factor, and conduit effects are not modeled — this is guidance, not an electrical-code calculation.