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Wire Size for 20 Amps
A 20-amp load at 240 V over a 100 ft run needs 10 AWG copper (30 A rating · 4.84 V drop (2%)). Change the distance or voltage to re-size.
Wire Size for 20 Amps
Minimum wire size30 A rating · 4.84 V drop (2%)
| Size | Ampacity | Voltage drop |
|---|---|---|
| 14 AWG | 20 A | 12.28 V (5.1%) |
| 12 AWG | 25 A | 7.72 V (3.2%) |
| 10 AWG | 35 A | 4.84 V (2%) |
| 8 AWG | 50 A | 3.06 V (1.3%) |
| 6 AWG | 65 A | 1.96 V (0.8%) |
| 4 AWG | 85 A | 1.23 V (0.5%) |
| 3 AWG | 100 A | 0.98 V (0.4%) |
| 2 AWG | 115 A | 0.78 V (0.3%) |
| 1 AWG | 130 A | 0.62 V (0.3%) |
| 1/0 AWG | 150 A | 0.49 V (0.2%) |
| 2/0 AWG | 175 A | 0.39 V (0.2%) |
| 3/0 AWG | 200 A | 0.31 V (0.1%) |
| 4/0 AWG | 230 A | 0.24 V (0.1%) |
| 250 kcmil | 255 A | 0.21 V (0.1%) |
| 300 kcmil | 285 A | 0.17 V (0.1%) |
| 350 kcmil | 310 A | 0.15 V (0.1%) |
| 500 kcmil | 380 A | 0.1 V (0%) |
NEC Table 310.16 (75 °C column), 240.4(D) small-conductor limits and Chapter 9 Table 8 resistance. Apply continuous-load (125%), ambient temperature and bundling corrections, and follow your local code and AHJ.
Planning estimates only. Building codes, loads and material specs vary — have a licensed engineer or contractor confirm quantities and safety requirements. Disclaimer
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