About the Amps to Volts Calculator
Amps cannot be converted to volts on their own, because current and voltage are different quantities. You need one more fact about the circuit: either the power in watts, or the resistance in ohms. This calculator offers both routes. With watts, it divides the power by the current, and for AC it also divides by the power factor and, for three-phase supplies, by the square root of three. With ohms, it applies Ohm's law, multiplying the current by the resistance. It shows the power the resistor dissipates and, for DC circuits, the resistance as well.
Updated October 2026
How to use the Amps to Volts Calculator
- 1Choose whether you know the power in watts or the resistance in ohms.
- 2Enter the current in amps.
- 3Enter the watts, type of current and power factor, or the resistance.
- 4Read the voltage in volts.
- 5Use the extra lines for the resistance or the heat dissipated.
Examples
A heating element rated 2,300 watts that draws 10 amps from a single-phase supply works at 230 volts. A 24 ohm lamp carrying 0.5 amps has 12 volts across it and dissipates 6 watts. A DC motor taking 15 amps with 180 watts of input is running at 12 volts.
If you only need a quick check, remember that doubling the current through a fixed resistor doubles the voltage across it and quadruples the heat produced.
In practice, the voltage you work out here is a design or checking number. Real supplies vary by several percent, and the voltage at a load falls when long cables carry a heavy current. If your calculated figure differs a lot from the rated voltage on the device, one of the inputs is probably wrong, or the load is not running at its rated power. Measuring with a meter under load is the only way to know what the equipment really receives.
Using the answer safely
- Never test mains circuits unless you are qualified.
- Use a multimeter rated for the voltage you expect.
- Check the power rating of resistors before passing current through them.
- Treat results as design numbers, not as measurements.
- Use the Voltage Drop Calculator for cables that carry a lot of current.
Related tools
The Ohm's Law Calculator solves for any one of voltage, current, resistance and power. The Watts, Amps, Volts Calculator relates all three, the Resistor Calculator handles series and parallel networks, and the Amps to Watts Calculator converts current to power.
Features
- Two methods: watts or ohms
- DC, single-phase and three-phase
- Power factor for AC loads
- Resistance and dissipated power shown
- Checks for zero current
- Free and offline-friendly
Frequently asked questions
Can you convert amps to volts?
Only with extra information. With power, volts equal watts divided by amps for DC, so 60 watts at 5 amps is 12 volts. With resistance, volts equal amps times ohms, so 5 amps through 24 ohms is 120 volts.
What is Ohm's law?
Voltage equals current times resistance, V = I × R. It links the three basic electrical quantities for a resistor. If you know any two of voltage, current and resistance, you can work out the third.
How do I find volts from watts and amps in AC?
Divide the watts by the amps and by the power factor. A single-phase load of 1,150 watts drawing 5 amps at a power factor of 1 runs from 230 volts. If the power factor were 0.8, the voltage would be 287.5 volts, which suggests the numbers are wrong.
What does a result that looks too high or low mean?
Common supply voltages are 5, 12, 24, 120, 230 and 400 volts. If your answer is far from these, check that the watts and amps belong to the same load and that you chose the right type of current.
How is voltage different from current?
Voltage is the push that drives charge round a circuit, measured in volts. Current is the amount of charge flowing, measured in amps. Think of voltage as pressure in a pipe and current as the flow of water.
Does this work for batteries?
Yes, for the load side. A 12 volt battery supplying 8 amps delivers 96 watts. For battery capacity and charge time use the mAh to Wh Calculator and the Battery Charge Time Calculator.