IT operations

Voltage Drop Calculator

Calculate the voltage drop across a conductor given current, length, and wire gauge. Use this Networking and IT tool to enter your numbers, review the result, and understand the key assumptions before making the next decision.

What you get
A focused calculator, clear explanation, common questions, and useful next tools.
Quick intro
Calculator
Result
Explanation
Common questions
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How this calculator works
The result depends on the numbers you enter and the assumptions shown below.

Voltage drop = 2 × Length × Current × Resistance per foot. For copper wire, resistance varies by AWG gauge. The NEC recommends keeping voltage drop below 3% for branch circuits.

Review the inputs carefully and treat the output as an estimate. For decisions involving money, taxes, health, law, or security, compare the result with trusted professional guidance when needed.

Frequently asked questions

What is acceptable voltage drop?

The NEC recommends no more than 3% voltage drop on branch circuits and 5% total (including feeders) for optimal performance.