Amps to Watts Calculator
Convert amps to watts — or watts to amps — from the voltage, in watts, kilowatts and amps.
Amps to watts is one multiplication — but it is the multiplication behind every circuit, breaker and cable. This calculator is that step, in both directions.
Enter the amps or watts and the volts; the answer follows.
Your results
Enter your measurements and press Calculate.
Quantities are rounded up to whole tiles, planks, boxes or bags, after the wastage allowance. Cost appears only when you enter a price.
Formula
All lengths are converted to a single unit before the calculation: 1 ft = 0.3048 m, 1 in = 25.4 mm, 1 ft² = 0.09290304 m², 1 yd² = 9 ft². Material quantities are rounded up — you cannot buy part of a tile, plank or bag.
How to use this calculator
- Choose the direction (Amps → Watts or Watts → Amps).
- Enter the amps (or watts) and the volts.
- Read the watts, kilowatts and amps.
Worked example
| Amps → Watts | 10 A × 240 V = 2,400 W = 2.4 kW |
|---|---|
| Watts → Amps | 1,500 W ÷ 120 V = 12.5 A |
Check it by hand: every step above uses the formula in the box. If your numbers match the example inputs but the calculator gives a different answer, please report it via the contact page.
Frequently asked questions
How many watts are 10 amps at 240 volts?
2,400 W (10 × 240). The same 10 amps at 120 V is only 1,200 W — voltage matters as much as current.
How many amps is a 1,500 W heater?
It depends on the voltage: 12.5 A at 120 V, 6.25 A at 240 V. Enter the watts and your voltage here.
What voltage do I use?
Your supply voltage — 120 V in the US, 230–240 V in the UK, EU and Australia. Check your supply or the device's label.
Is this a substitute for electrical design?
No. This is a conversion for planning. Circuit sizing and electrical safety require qualified professionals and local code compliance — see the safety notice.
Related calculators
Estimates only. Results are for planning. Measure twice, confirm box coverage and tile sizes on the packaging you buy, and follow the manufacturer's instructions. See the disclaimer.