Watts to Amps Calculator
Convert watts to amps for DC and AC circuits, and check the load against common breaker sizes.
The 80% rule
Continuous loads — anything running for three hours or more — should not exceed 80% of a breaker's rating under the NEC. A 15 A circuit therefore carries 12 A continuously, or about 1,440 W at 120 V. That is why a 1,500 W space heater trips a shared kitchen circuit: the heater alone is at the limit before anything else is plugged in.
How to use the Watts to Amps Calculator
- Fill in each field with your own figures — the defaults are only there as an example.
- The result updates as you type, so there is no button to press.
- Check the breakdown under the main result for the supporting numbers.
- Use the copy button to take the result with you, or share the link to reload the same inputs.
Watts to Amps Calculator — frequently asked questions
Is this watts to amps calculator free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
How accurate is the result?
The maths is exact for the formula shown on the page. Accuracy in the real world depends on your inputs and on assumptions the formula cannot see, so treat the output as a well-grounded estimate rather than a quote.
Can I use it on my phone?
Yes. The page is responsive, weighs a few kilobytes and works offline once loaded, so it behaves the same on a phone as on a desktop.
Focused versions of this calculator
Each of these does one specific job with its own defaults and explanation.
- Three Phase Watts to Amps Calculator Three-phase power with the √3 factor and power factor applied.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 15, 2026 · Calculation runs client-side · No data collected · Report an error