The Cable Length Calculator tells you the maximum one-way distance a given wire can run while staying within an allowed voltage drop, for a set current and voltage.
Cable Length Calculator (Max Run)
Find the maximum one-way cable length for a given wire size, current, voltage and allowed voltage drop. Works for copper, aluminum, single and three phase.
Inputs
Result
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max one-way (ft)
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max one-way (m)
About Cable Length Calculator (Max Run)
Features
- Pick any AWG or kcmil
- Copper or aluminum
- Single or three phase
- Tunable allowed drop
How to Use
- Choose wire size, material, phase and voltage.
- Enter current and allowed drop percent.
- Read the maximum one-way length.
Examples
Example: 10 AWG copper, 30 A, 240 V, 3% drop, single phase -> about 103 ft.
Benefits
- Check if a wire reaches the load
- Plan feeder and branch runs
Frequently Asked Questions
What does this tool find?
It returns the longest one-way run for a chosen wire size before voltage drop exceeds your limit.
Why one-way length?
Electrical runs are described by the one-way (source to load) distance. The calculator already accounts for the return conductor.
Does phase change the result?
Yes. Three-phase runs tolerate a longer distance for the same drop because of the sqrt(3) factor.
Is my data saved?
No. All math runs in your browser.