Watts to Amps Calculator
Convert electrical power (watts) and voltage to current in amps for DC, single-phase AC, and three-phase AC. Includes power factor for AC. All calculations run in your browser.
Real power in watts (not VA).
Volts across the load.
Table of Contents
Why convert watts to amps?
Equipment nameplates and energy bills often list power in watts, but breakers, fuses, and wire sizes are chosen from current in amps. Converting watts to amps tells you how much current a load draws (or should draw) at a given voltage.
For DC, current is simply I = P ÷ V. For AC, you must include the power factor when converting real power (watts) to current, because not all apparent power becomes real work.
Single-phase: I = P ÷ (VRMS × PF). Balanced three-phase with line-to-line voltage: I = P ÷ (√3 × VL-L × PF).
Use the same RMS and line-to-line assumptions as in our Amps to Watts Calculator — these two tools are exact inverses when inputs are consistent.
Formulas
DC
I (A) = P (W) ÷ V (V)
Power factor does not apply to DC.
AC single-phase
I (A) = P (W) ÷ (VRMS × PF)
Use RMS voltage (what multimeters and outlet ratings show). PF is typically 0.8–1 for many loads.
AC three-phase (balanced)
I (A) = P (W) ÷ (√3 × VL-L × PF)
VL-L is line-to-line RMS voltage. √3 ≈ 1.732. If you only know line-to-neutral voltage: VL-L = VL-N × √3 before using this form, or use I = P ÷ (3 × VL-N × PF) per line in a balanced wye.
Quick Reference Table
| Type | Watts | Voltage | PF | Amps | Typical load |
|---|---|---|---|---|---|
| DC | 120 W | 12 V | — | 10 A | Car electronics |
| DC | 240 W | 48 V | — | 5 A | E-bike motor |
| AC 1-phase | 1,080 W | 120 V | 0.9 | 10 A | Toaster (US) |
| AC 1-phase | 2,070 W | 230 V | 0.9 | 10 A | Kettle (AU/EU) |
| AC 1-phase | 4,140 W | 230 V | 0.9 | 20 A | Electric oven |
| AC 3-phase | 6,462 W | 415 V | 0.9 | 10 A | Industrial motor (AU) |
| AC 3-phase | 20,679 W | 415 V | 0.9 | 32 A | Commercial load |
FAQ
Only for DC or when you treat AC as a rough estimate with PF = 1. For real AC loads, divide by V × PF (single-phase) or √3 × VL-L × PF (three-phase line-to-line).
If you ignored power factor, you may have underestimated current. Lower PF means more current is needed to deliver the same real power in watts.
Enter power in watts (multiply kW by 1000). Example: 2.5 kW → type 2500.
They use the same physics in reverse. Amps × volts (with PF and √3 as appropriate) gives watts; watts ÷ the same denominator gives amps.