Volts to amps calculator
To get amps from volts you need one more number: the load’s watts or its resistance. Pick which one you know.
VC-2 converterV → A
Supply
W
V
1 for heaters; ~0.85 motors
Current5A
I = P ÷ (V × PF)Breaker: 15 A non-continuous · 15 A if it runs 3 h+
Breaker figures are the next standard size from NEC 240.6(A), with 125% for continuous loads (210.20(A)). The wire must be rated for the breaker, and motors and HVAC follow different rules. See the breaker size calculator.
Quick reference
| Watts | 12 V DC | 120 V | 240 V |
|---|---|---|---|
| 100 W | 8.33 | 0.83 | 0.42 |
| 500 W | 41.67 | 4.17 | 2.08 |
| 1,000 W | 83.33 | 8.33 | 4.17 |
| 1,500 W | 125 | 12.5 | 6.25 |
| 2,000 W | 166.7 | 16.67 | 8.33 |
| 2,500 W | 208.3 | 20.83 | 10.42 |
| 3,000 W | 250 | 25 | 12.5 |
| 4,000 W | 333.3 | 33.33 | 16.67 |
| 5,000 W | 416.7 | 41.67 | 20.83 |
| 7,500 W | 625 | 62.5 | 31.25 |
| 10,000 W | 833.3 | 83.33 | 41.67 |
Amps at power factor 1 (resistive loads).
The formulas
DC: P = V × I, so I = P ÷ V
AC single-phase: P = V × I × PF, so I = P ÷ (V × PF)
AC three-phase: P = 1.732 × VLL × I × PF, so I = P ÷ (1.732 × VLL × PF)
PF is power factor, between 0 and 1. Resistive loads (heaters, incandescent lamps, water heaters) are 1. Motors, compressors and power supplies are lower, which means they draw more current for the same watts.
Using the result safely
- Nameplate current beats a calculation. If the equipment lists amps, use that figure.
- For a load that runs 3 hours or more (EV charger, water heater, space heater), the NEC sizes conductors and breakers at 125% of the load.
- To pick the conductor for the current you found, go to the wire size calculator; for long runs check the voltage drop.
Questions people ask
How do I convert volts to amps?
With watts: I = P ÷ V (single-phase AC divide by PF too). With resistance: I = V ÷ R.
How many amps is 240 volts?
Voltage by itself has no current. A 4,800 W water heater on 240 V draws 20 A; a 240 V, 30 A dryer circuit can deliver 7,200 W.