Quick start
- Enter the current in amps from the device label, meter, or specification.
- Enter the supply voltage, such as 12 V DC, 120 V, 240 V, 208 V, or 480 V.
- Choose DC, single-phase AC, or three-phase AC, then enter power factor for AC loads when you know it.
Best uses
Start here if one of these sounds like your job. The examples below show which inputs matter most.
- Estimate watts from a current draw.
- Convert a circuit amp value into rough power.
- Compare single-phase and three-phase examples.
- Understand when voltage, phase, or power factor changes AC watts.
What this calculator is solving
The Amps to Watts Calculator turns current, voltage, phase type, and power factor into a real-power estimate. It is handy when you know current draw and voltage and want a rough watt or kilowatt number.
Match each input label on the calculator to the current in amps, supply voltage, DC or AC phase type, and power factor from the device label or specification when it is available.
The formula in plain language
In plain language: DC watts = amps x volts. Single-phase AC watts = amps x volts x power factor. Three-phase AC watts = amps x volts x sqrt(3) x power factor. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
For DC, watts = amps x volts. For single-phase AC, multiply by power factor. For three-phase AC, multiply by sqrt(3) and power factor.
How to read the answer
Read watts as the estimated real power. Read kilowatts when the number is large enough that a 1.5 kW or 6.12 kW comparison is easier than a watt-only answer.
- The main answer is estimated watts.
- The kilowatts metric is the same result divided by 1,000.
- Power factor and phase type explain why equal amps can create different watt values.
- Use the result for comparison or planning before checking equipment instructions and safety requirements.
Common mistakes to avoid
Most amps-to-watts mistakes come from ignoring voltage, assuming every AC load has power factor 1, or using a simple power estimate as if it were a wiring approval.
- Do not assume all AC loads have power factor 1.
- Do not compare amperage without checking voltage.
- Do not use this as a final breaker, wire, extension-cord, motor, appliance, or code calculation.
Quick 120 V example
Say a space heater draws 12.5 A on a 120 V circuit and the power factor is 1. Multiply 12.5 by 120 to get 1,500 W.
That is the same as 1.5 kW after dividing by 1,000. This is a useful comparison number when you are estimating load, energy use, or whether two devices are in the same power range.
Why phase and power factor change the answer
A 10 A single-phase motor at 240 V with 0.9 power factor is about 2,160 W. The same 10 A at a different voltage or power factor would not mean the same watts.
A 20 A three-phase load at 208 V with 0.85 power factor is about 6,124 W, or 6.12 kW. The three-phase formula includes sqrt(3), so using simple DC math would understate the result.
- Use DC math only for DC loads.
- Use the equipment power factor when accuracy matters.
- Use manufacturer data and a qualified professional for circuit sizing, code compliance, and electrical safety.
Research and references
These references help check the measurements, units, limits, or safety notes used in this guide.
Worked examples for Amps to Watts Calculator
1,500 W, or 1.5 kW
2,160 W, or 2.16 kW
About 6,124 W, or 6.12 kW
FAQ in plain language
When should I use the Amps to Watts Calculator?
Use it when your task matches one of these common needs: Estimate watts from a current draw. Convert a circuit amp value into rough power. It works best when you already know the measurements, amounts, units, or options the page asks for.
What is the Amps to Watts Calculator doing with my inputs?
In plain language: DC watts = amps x volts. Single-phase AC watts = amps x volts x power factor. Three-phase AC watts = amps x volts x sqrt(3) x power factor. The examples on the page are there so you can compare your inputs with a worked example before copying the answer.
What do the main Amps to Watts Calculator inputs mean?
Amps: current drawn by the device or circuit, usually from a nameplate, meter, or specification. Volts: the supply voltage used by the load, such as 12 V DC, 120 V, 240 V, 208 V, or 480 V. Phase: DC, single-phase AC, or three-phase AC formula selection. Power factor: AC correction factor used to estimate real watts from apparent volt-amps.
How should I read the Amps to Watts Calculator answer?
Read the headline answer, then check the supporting lines and examples to understand how the calculator got there. If one input changes, rerun the tool and compare the new answer instead of guessing.
What should I double-check before trusting the answer?
This is a simplified electrical estimate for planning and comparison. Starting surge, code rules, conductor size, breaker size, duty cycle, and equipment nameplate limits still need manufacturer data and qualified electrical review. Also check the unit, scale, mode, and result limit because small input changes can change the answer.
Is amps to watts always amps times volts?
For DC, watts are amps times volts. For single-phase AC, multiply amps by volts and power factor. For three-phase AC, also multiply by the square root of 3.
Why does the same amperage give different watts?
Voltage, phase, and power factor all change the answer. Ten amps at 12 volts is very different from ten amps at 240 volts or 480 volt three-phase service.
Related tools
- Watts to Amps Calculator Convert watts to amps with voltage, phase type, and power factor.
- Ohm's Law Calculator Solve voltage, current, resistance, and power from two known circuit values.
- Electricity Calculator Estimate electricity use and cost from watts, hours, days, and rate per kWh.
Keep exploring
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Privacy and copying results
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Use Copy answer when you want to save the inputs and result in notes, homework, a message, or a project list. Check the units, labels, and limits before copying.