Amps to Watts Calculator — P = I × V (Free)

Convert amps to watts from voltage — reverse for watts to amps

Operating Mode

Required Parameters

Current

Voltage

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Quick Answer

Watts = amps × volts. 10 A at 120 V = 1,200 W; 15 A at 240 V = 3,600 W. Reverse: amps = watts ÷ volts.

Documentation

Amps to Watts Calculator

Convert amps to watts with P = I × V. Enter current and voltage — the calculator returns watts and the implied resistance. Switch to Watts to Amps for the reverse.

Quick start: 10 A at 120 V → 1,200 W. 15 A at 240 V → 3,600 W.

Amps to watts formula

P = I × V

Current	Voltage	Power
1 A	120 V	120 W
5 A	120 V	600 W
10 A	120 V	1,200 W
15 A	120 V	1,800 W
10 A	240 V	2,400 W
20 A	240 V	4,800 W

Watts to amps

I = P / V

A 1,800 W appliance on 120 V draws 15 A. On 240 V it draws 7.5 A.

AC, power factor, and three-phase

This converter is real power at PF = 1 (DC or resistive AC). Motors and supplies with a nameplate in VA or kVA belong on the Volts to Amps Calculator (VA to amps) or the three-phase calculator.

Related tools

Volts to Amps Calculator
Amps Watts Volts Converter — all four modes
Electrical Power Calculator
Ohm's Law Calculator

Design Notes

You cannot convert volts to amps with voltage alone — power or resistance must be known. P = V × I is real power for DC and for AC at power factor 1. VA is apparent power; on three-phase systems line current uses √3. For resistive DC loads you can also use I = V / R or P = I²R.

Common Mistakes

1
Trying to convert volts to amps without watts, VA, or resistance — the units are not interchangeable by themselves.
2
Using P = V × I on a three-phase feeder without the √3 factor. Three-phase real power is √3 × VL × IL × PF.
3
Treating VA as watts when the load power factor is not 1. Watts = VA × PF.

Engineering Handbox

1. P = I × V 2. P = 10 × 120 = 1200 W

Verification10 A at 120 V is 1.2 kW. Reverse: I = 1200 / 120 = 10 A.

Knowledge Base

How do I convert amps to watts?

Multiply current by voltage: P(W) = I(A) × V(V). Example: 8 A on a 120 V circuit is 960 W. This is real power at power factor 1 (DC or resistive AC).

What is 10 amps to watts at 120 V?

10 × 120 = 1,200 watts (1.2 kW). At 240 V the same 10 A is 2,400 W. Voltage must be known — amps alone do not define watts.

How do I convert watts back to amps?

Use Watts to Amps on this page: I = P / V. A 1,800 W kettle on 120 V draws 15 A. On 240 V it draws 7.5 A.

Does this work for AC motors and three-phase?

For single-phase resistive loads, yes. Motors and other inductive loads need power factor: watts = V × I × PF. For apparent current from a nameplate in VA or kVA, use the volts-to-amps page (VA to amps) or the three-phase calculator.

What if I know current and resistance but not voltage?

Use P = I²R. Example: 2 A through 6 Ω is 24 W. The electrical power calculator solves that form; this page is the converter people search as amps to watts.

How many watts is 15 amps at 120 V?

15 × 120 = 1,800 W. That is why a typical US 15 A household branch is treated as a 1,800 W budget (80% continuous = 1,440 W).

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