Voltage Drop Calculator
Calculate the voltage drop across a DC wire run based on current, wire resistance, and length.
Calculate
Enter your values below.
Result
Voltage drop
0
Formula used
Voltage drop = 2 × Current × Resistance per 1000ft × (Length ÷ 1000)
Example: 10 A over a 50 ft run at 2 Ω/1000ft → voltage drop = 2 V.
How to use this calculator
- Enter Current (A), Wire resistance (Ω per 1000 ft), One-way wire length (ft).
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
Why is the length multiplied by 2?
Current flows out and back through the circuit, so the round-trip wire length is double the one-way distance.
Where do I find wire resistance per 1000 ft?
Standard wire gauge (AWG) resistance tables list this value for each gauge and material.
What voltage drop is acceptable?
A common guideline is keeping voltage drop under 3% of the supply voltage for most circuits.
Does this work for AC circuits?
This is a simplified DC-style calculation; AC circuits with significant reactance need a more detailed analysis.