Amps to Watts

Convert electrical current in amps to power in watts using voltage and power factor. Free, instant, no signup.

Current (amps)

Voltage (volts)

Power factor

Formula: Watts = amps × volts × power factor

How to use the Amps to Watts

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About the Amps to Watts

The Amps to Watts converter turns a current reading in amperes into electrical power in watts, but only once you tell it the voltage. Amps measure how much current flows; watts measure how much work that current actually does. The two are linked by the voltage pushing the current along, which is why this tool always asks for volts alongside amps. Drop in a 5 A reading at 120 V and you get 600 W; the same 5 A at 240 V gives 1,200 W. That dependence on voltage is the single most important thing to understand, and it is exactly what this converter handles for you.

Reach for this tool whenever you need to know the real load a device places on a circuit. Electricians and DIYers use it to check whether appliances will overload a breaker: a 15 A breaker on a 120 V line tops out near 1,800 W, and a 20 A circuit at 120 V around 2,400 W. RV owners, van builders, and solar hobbyists use it to size inverters, wiring, and charge controllers from a battery's amp draw, since 12 V, 24 V, and 48 V systems all behave differently. It is also handy for reading equipment nameplates where current is listed but wattage is not.

Under the hood, the converter uses the standard power equation. For DC and for purely resistive AC loads like heaters or incandescent bulbs, watts = amps x volts. For other AC loads it multiplies in the power factor (watts = amps x volts x power factor), and for three-phase supplies it adds a factor of the square root of 3 for line-to-line voltage. Power factor reflects how much current does useful work: resistive loads sit at 1.0, while motors and pumps often run between 0.7 and 0.9. Choosing the correct circuit type and power factor is what keeps the result honest.

Results are only as accurate as the figures you enter, so use the actual measured or nameplate voltage and a realistic power factor rather than a guess; an assumed PF of 1.0 on a motor load will overstate the watts. Treat the output as a planning and sizing estimate, not a substitute for a clamp meter or a licensed electrician on safety-critical work. The whole calculation runs in your browser using simple arithmetic, so your voltage, current, and power numbers never leave your device or get stored on a server.

Frequently asked questions

Why does this converter need the voltage and not just the amps?

Watts measure power, which depends on both current and the voltage driving it, so amps alone cannot give you watts. The same current produces very different power at 12 V, 120 V, or 240 V, which is why voltage is a required input.

What is the formula to convert amps to watts?

For DC and resistive AC loads it is watts = amps x volts. For AC loads with a power factor, watts = amps x volts x power factor, and for three-phase line-to-line supplies you multiply by an additional square root of 3.

What power factor should I use?

Use 1.0 for purely resistive loads such as electric heaters, toasters, and incandescent bulbs. Motors, pumps, and many electronics run lower, typically 0.7 to 0.9, so check the device nameplate or use about 0.8 for a general motor estimate.

How many watts is 15 amps?

It depends on voltage. At 120 V, 15 A is 1,800 W; at 240 V the same 15 A is 3,600 W. This is why a 15 A breaker on a standard 120 V circuit is usually rated for roughly 1,800 W of load.

Should I use DC or single-phase for a car or solar battery?

Batteries supply direct current, so choose DC and enter the system voltage, such as 12 V for most cars or 24 V and 48 V for many solar setups. The converter then uses the simple watts = amps x volts formula with no power factor.

From our blog

Fluid Ounces to Cups: The 8-to-1 Rule and When It Breaks

By the Super Simple Digital Tools Team · Updated June 2026

Almost every kitchen conversion between fluid ounces and cups rests on a single fact: in the US system, one cup holds eight fluid ounces. Lock that ratio in and the rest is just division. Sixteen fluid ounces is two cups, four fluid ounces is half a cup, and two fluid ounces is a quarter cup. Once the 8-to-1 rule feels automatic, you can read a recipe written in either unit and translate on the fly without reaching for a calculator at all.

The reason a tool still helps is that real-world numbers rarely land on clean cup boundaries. Beverage cans and food cartons are sized for marketing and shipping, not for tidy fractions, so you end up with quantities like 12, 20, or 24 fluid ounces. Twelve divides into 1.5 cups and twenty into 2.5 cups, but odd figures such as 7 or 22 fluid ounces produce decimals that are awkward to eyeball at the counter. Entering the exact number and reading back the precise cup value removes that guesswork.

There is one trap that catches cooks who work from international recipes: not all cups are equal. The US cup is 8 fluid ounces, roughly 237 milliliters, while the UK imperial cup is 10 fluid ounces, about 284 milliliters, making it nearly 20 percent larger. The fluid ounces themselves differ too, with the US fluid ounce around 4 percent bigger than the imperial one. In baking, where ratios of liquid to flour decide texture, that gap can be the difference between a tender crumb and a dense, wet result.

Keep firmly in mind that this conversion is for liquids measured by volume. A fluid ounce is a measure of space, but a plain ounce on a food label is usually a measure of weight. Eight ounces of water happens to fill one cup, but eight ounces of flour by weight occupies far more than a cup of space, because flour is lighter than water. Whenever a recipe lists dry ingredients in ounces, treat that as weight and use a kitchen scale or an ingredient-specific chart rather than this volume converter.

Put together, the workflow is fast and reliable. Identify whether your figure is a liquid volume in US fluid ounces, type it in, and read the cup value. Use the result to fill a standard liquid measuring cup, checking at eye level for the most accurate read. For anything written in imperial cups or measured by weight, switch to the matching tool. Within those boundaries, fluid ounces to cups is one of the most dependable conversions in any kitchen.

Memorize three anchors: 8 fl oz = 1 cup, 16 fl oz = 2 cups, 4 fl oz = half a cup. Most other amounts are easy to interpolate from these.
When a result is a decimal like 0.75 cup, translate it to fractions you can measure: 0.75 is three-quarters and 0.25 is one-quarter of a cup.
If a recipe comes from a British or Australian source, confirm whether it uses imperial or metric cups before trusting an 8-to-1 conversion.
Use a liquid measuring cup with a spout and read the meniscus at eye level; dry measuring cups are not meant for accurate liquid volumes.

Read the full guide →

Tool by the Super Simple Digital Tools Team. Reviewed by our editorial team. Free to use, no signup required.