LumaQuote Electrical calculators Amps to watts

Amps to Watts Calculator

Convert amps to watts for single-phase, three-phase and DC. Enter the current and voltage, add the power factor for AC loads, and get the power in watts and kilowatts.

How to convert amps to watts

Power is volts times amps. On AC circuits, multiply by the power factor to get real power in watts. Three-phase adds the square root of 3 (1.732).

DC: watts = amps × volts

Single-phase AC: watts = amps × volts × power factor

Three-phase AC: watts = 1.732 × amps × line-to-line volts × power factor

Examples

15 A at 120 V: 15 × 120 = 1,800 W at power factor 1.0.
30 A at 240 V: 30 × 240 = 7,200 W.
100 A three-phase at 480 V, power factor 0.9: 1.732 × 480 × 100 × 0.9 = 74,825 W, or 74.8 kW.

Amps to watts chart

Power at common voltages, power factor 1.0. For other loads, multiply the watts shown by the power factor.

Amps	120 V	208 V	240 V	277 V	208 V 3-phase	480 V 3-phase
1 A	120 W	208 W	240 W	277 W	360 W	831 W
2 A	240 W	416 W	480 W	554 W	721 W	1,663 W
5 A	600 W	1,040 W	1,200 W	1,385 W	1,801 W	4,157 W
10 A	1,200 W	2,080 W	2,400 W	2,770 W	3,603 W	8,314 W
15 A	1,800 W	3,120 W	3,600 W	4,155 W	5,404 W	12,471 W
20 A	2,400 W	4,160 W	4,800 W	5,540 W	7,205 W	16,628 W
25 A	3,000 W	5,200 W	6,000 W	6,925 W	9,007 W	20,785 W
30 A	3,600 W	6,240 W	7,200 W	8,310 W	10,808 W	24,942 W
40 A	4,800 W	8,320 W	9,600 W	11,080 W	14,411 W	33,255 W
50 A	6,000 W	10,400 W	12,000 W	13,850 W	18,013 W	41,569 W
60 A	7,200 W	12,480 W	14,400 W	16,620 W	21,616 W	49,883 W
100 A	12,000 W	20,800 W	24,000 W	27,700 W	36,027 W	83,138 W

Three-phase columns use the line-to-line voltage and the current per line.

Watts vs volt-amps

Volts × amps gives volt-amps (VA), the apparent power the wiring carries. Watts are the real power the load turns into heat, light or motion. They are equal only when the power factor is 1.0. Transformers, UPS units and generators are rated in VA or kVA for that reason; the kVA calculator works in kVA.

How much power a circuit can carry

A breaker's rating times the voltage is the most the circuit can carry. Loads that run for 3 hours or more (lighting, heaters, EV chargers) are continuous, and continuous loads are limited to 80% of the breaker rating.

Circuit	Maximum	Continuous (80%)
15 A at 120 V	1,800 W	1,440 W
20 A at 120 V	2,400 W	1,920 W
20 A at 277 V	5,540 W	4,432 W
30 A at 240 V	7,200 W	5,760 W

At power factor 1.0. With a lower power factor, the watts drop by that factor.

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Amps to watts FAQ

How many watts is 15 amps?

1,800 W at 120 V. For a continuous load such as lighting or a heater, plan on 80% of that, 1,440 W.

How many watts is 20 amps at 240 volts?

4,800 W at power factor 1.0, or 3,840 W for a continuous load.

How many watts is 30 amps?

3,600 W at 120 V and 7,200 W at 240 V, at power factor 1.0.

How do you convert amps to kW on three-phase?

Multiply 1.732 × line-to-line volts × amps × power factor, then divide by 1,000. 100 A at 480 V is 83.1 kW at power factor 1.0, or 74.8 kW at 0.9.

What is the difference between watts and VA?

VA is volts times amps, the power the wiring carries. Watts are the power the load actually uses. Watts = VA × power factor, so they match only at power factor 1.0.

Do I need the power factor?

For DC and for resistive AC loads like heaters, no: use 1.0. For motors, LED drivers and other electronic loads, yes. Without it you get volt-amps, not watts.