Which formula should I use?

Use Ohm's Law (I = V / R) when you know the resistance of the load. Use the power formula (I = P / V) when you know the power consumption (wattage) and supply voltage instead.

Does this work for AC circuits?

For purely resistive AC loads both formulas apply directly. For reactive loads (inductors or capacitors) you would need impedance in place of resistance, but the arithmetic is identical.

What units should I enter?

Voltage in volts (V), resistance in ohms (Ω), and power in watts (W). The result is always in amperes (A).

Why does the result show "—" instead of a number?

A result cannot be computed if any required input is zero, empty, or non-numeric. Fill in both fields with positive numbers to see a result.

How do I convert milliamps to amps?

Divide milliamps by 1000. For example, 500 mA = 0.5 A. Enter the value in amps (e.g. 0.5) when using this calculator.

Volts to Amps Calculator

Name: Volts to Amps Calculator
Availability: InStock
Author: Nham Vu

Convert volts to amps using Ohm's Law (I = V / R) or the power formula (I = P / V).

Formula

Voltage (V)

Resistance (R)

Ω

Enter values on the left to calculate current

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Summary

Convert volts to amps using Ohm's Law (I = V / R) or the power formula (I = P / V).

How it works

Select the formula you want to use.
For Ohm's Law, enter voltage in volts and resistance in ohms; current is calculated as I = V / R.
For the power formula, enter power in watts and voltage in volts; current is calculated as I = P / V.
Results update instantly as you type.
Click Copy Result to copy the computed amperage to your clipboard.

Use cases

Determine how many amps a device draws given its supply voltage and resistance.
Calculate current consumption of an appliance from its wattage and supply voltage.
Size fuses and circuit breakers correctly for a given load.
Verify wire gauge requirements based on expected current draw.
Check electrical specifications on datasheets and product manuals.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu