Ohm's Law states that the current (I) through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R): I = V / R.

How do I convert ohms to amps?

You cannot convert ohms to amps directly without knowing the voltage. Use the formula I = V / R, where I is current in amps, V is voltage in volts, and R is resistance in ohms.

What if my resistance is zero?

A resistance of zero would imply a short circuit, resulting in theoretically infinite current. The calculator will warn you if you enter zero or a negative resistance.

Can I use milliamps or kilohms?

Yes. Use the unit dropdowns next to each field to select milliamps (mA), microamps (µA), kilohms (kΩ), megaohms (MΩ), millivolts (mV), or kilovolts (kV). The calculator converts automatically.

Does this work for AC circuits?

This tool calculates DC resistance using Ohm's Law. For AC circuits with reactive components (inductors, capacitors), you would need to use impedance (Z) instead of pure resistance (R), which is beyond this tool's scope.

Ohms to Amps Calculator

Enter voltage (V) and resistance (R) to calculate current in amps using Ohm's Law: I = V / R.

Ohm's Law Calculator

Select what to solve for, then enter the two known values.

Voltage

Resistance

Ohm's Law Formulas

I = V / R Current = Voltage / Resistance

V = I × R Voltage = Current × Resistance

R = V / I Resistance = Voltage / Current

Enter values and press Calculate to see the result.

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Summary

This calculator applies Ohm's Law (I = V / R) to convert a known voltage and resistance into the resulting current in amperes. It supports three solve modes: calculate current from voltage and resistance, calculate voltage from current and resistance, or calculate resistance from voltage and current. Click Calculate or press Enter to update the result.

How it works

Select the quantity you want to calculate: Current (I), Voltage (V), or Resistance (R).
Enter the two known values into the corresponding fields.
The calculator applies Ohm's Law and displays the result instantly.
Use the unit selectors to work in milliamps, kilohms, millivolts, and more.
Copy the result with one click for use in your project notes.

Use cases

Determine the current draw of a resistor in a circuit given supply voltage.
Find the correct resistor value to limit current to an LED.
Calculate how much voltage drop occurs across a known resistance.
Verify electrical component ratings before assembly.
Educational use: demonstrate Ohm's Law relationships interactively.
Quick field checks during electronics prototyping and debugging.

Frequently Asked Questions

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