Voltage Drop Chart
Max one-way distance per wire size — interactive, NEC-based. No more squinting at PDFs.
Max distance (ft, one-way)
| Wire size | Max distance |
|---|
Highlighted row = smallest wire that reaches ≥100 ft under these conditions. Distances are one-way; double for round-trip.
How it's computed
Lmax = (limit% × V × CM) ÷ (2 × K × I) for single-phase (√3 for three-phase) — the voltage-drop formula solved for distance, per NEC Chapter 9, Table 8 (K = 12.9 copper / 21.2 aluminum).
- NEC 210.19(A) informational note: 3% max on branch circuits, 5% feeder + branch combined.
- Need the drop for a fixed run instead? Use the voltage drop calculator.