Watts to Amps Calculator
Convert power to current (or back) for DC, AC single-phase and three-phase systems. Enter the value and your voltage — the rest is instant.
Use ~1.0 for resistive loads (heaters), ~0.8–0.9 for motors and mixed loads.
Three-phase uses line-to-line voltage. Motor start-up surges draw several times these figures briefly.
How this conversion works
Amps = Watts ÷ Volts.For AC single-phase:
Amps = Watts ÷ (Volts × PF).For AC three-phase:
Amps = Watts ÷ (√3 × Volts × PF).Reverse the formula to go from amps back to watts. Apparent power (kVA) = real power (kW) ÷ power factor.
Turning watts into amps
Power (watts) and current (amps) are linked by voltage: for a simple DC circuit, current is just power divided by voltage. Add alternating current and the power factor enters — the fraction of the supplied power that does useful work. Motors and other inductive loads have a power factor below 1, so they draw more current than their wattage alone suggests. That is why you size breakers, wire and inverters around amps, not watts.
A worked example
A 1,000 W load on a 230 V single-phase supply at 0.9 power factor draws 1,000 ÷ (230 × 0.9) ≈ 4.83 A. The same 1,000 W on 12 V DC draws 1,000 ÷ 12 ≈ 83 A — which is why low-voltage DC needs such thick cable.
Frequently asked questions
Divide watts by volts for DC or resistive loads. For AC, divide by volts times the power factor (single-phase), or by the square root of 3 times volts times power factor for three-phase.
Use 1.0 for purely resistive loads such as heaters and incandescent bulbs, and roughly 0.8 to 0.9 for motors, pumps, air conditioners and mixed household loads.
Because amps equal watts divided by volts. At a lower voltage you need far more current to move the same power, which is why 12V systems require much heavier wiring than 230V ones.
This is the steady running current. Motor-driven loads briefly draw a start-up surge several times higher, which you must allow for when sizing inverters, generators and breakers.
Sources & standards
These watts/amps/volts conversions follow standard SI unit definitions and the electrical-code power-factor conventions referenced below.
- The International System of Units (SI) — National Institute of Standards and Technology
Defines the watt, ampere and volt this calculator converts between. - NFPA 70 — National Electrical Code (NEC) — National Fire Protection Association
Source of the single-phase and three-phase current formulas, and the practice of sizing wiring and breakers to amps rather than watts. - NEMA MG 1 — Motors and Generators — National Electrical Manufacturers Association
Reference for the 0.8–0.9 power-factor range this calculator suggests for motor and pump loads.