Voltage drop calculator
Enter the circuit and the one-way length of the run. You get the drop for the size you pick and the smallest size that stays at or under your target.
Result
7.92 V, 6.60 percent. Smallest size for this load at or under 3.00 percent: 8 AWG
- Voltage drop, 12 AWG
- 7.92 V, 6.60 percent
- At the load
- 112.08 V
- Smallest size for this load at or under 3.00 percent
- 8 AWG
| Size | Drop (V) | Drop (%) | Max load (A), 60 C |
|---|---|---|---|
| 18 AWG | 31.80 | 26.50 | cord size |
| 16 AWG | 19.96 | 16.63 | cord size |
| 14 AWG | 12.56 | 10.47 | 15 |
| 12 AWG | 7.92 | 6.60 | 20 |
| 10 AWG | 4.96 | 4.13 | 30 |
| 8 AWG, meets target | 3.11 | 2.59 | 40 |
| 6 AWG | 1.96 | 1.64 | 55 |
| 4 AWG | 1.23 | 1.03 | 70 |
| 3 AWG | 0.98 | 0.82 | 85 |
| 2 AWG | 0.78 | 0.65 | 95 |
| 1 AWG | 0.62 | 0.51 | 110 |
| 1/0 AWG | 0.49 | 0.41 | 125 |
| 2/0 AWG | 0.39 | 0.32 | 145 |
| 3/0 AWG | 0.31 | 0.26 | 165 |
| 4/0 AWG | 0.24 | 0.20 | 195 |
| 250 kcmil | 0.21 | 0.17 | 215 |
| 300 kcmil | 0.17 | 0.14 | 240 |
| 350 kcmil | 0.15 | 0.12 | 260 |
| 400 kcmil | 0.13 | 0.11 | 280 |
| 500 kcmil | 0.10 | 0.09 | 320 |
| 600 kcmil | 0.09 | 0.07 | 350 |
| 700 kcmil | 0.07 | 0.06 | 385 |
| 750 kcmil | 0.07 | 0.06 | 400 |
| 800 kcmil | 0.06 | 0.05 | 410 |
| 900 kcmil | 0.06 | 0.05 | 435 |
| 1000 kcmil | 0.05 | 0.04 | 455 |
Uses stranded conductor resistance at 75 C from NEC Chapter 9, Table 8. Single phase and DC: 2 x I x R x L. Three phase: 1.732 x I x R x L. AC reactance, which adds a little on large conductors in steel conduit, is not included. Max load comes from the ampacity column you pick, with 14, 12 and 10 AWG copper held to 15, 20 and 30 A (12 and 10 AWG aluminum to 15 and 25 A). NM-B and UF-B are held to the 60 C column. A continuous load needs 125 percent, and more than three conductors or high heat lower it.
Use it to size a run, then check the size against your local code or with a licensed electrician.