What formula converts volts to ohms?

When current is known: R = V / I (Ohm's Law). When power is known: R = V² / P. Both formulas are derived from the fundamental relationship V = I × R.

Voltage in volts (V), current in amperes (A), power in watts (W), and resistance in ohms (Ω).

Can I enter millivolts or milliamps?

Convert to base units first: 500 mV = 0.5 V, 200 mA = 0.2 A. Then enter those decimal values into the calculator.

What happens if current or power is zero?

Division by zero is undefined in both formulas. The calculator will display an error if either divisor is zero.

Does this work for AC circuits?

For AC circuits the result is impedance magnitude rather than pure resistance. Use it as an approximation for purely resistive loads only.

How is this different from an amps-to-ohms calculator?

The underlying formula is the same (R = V / I), but here voltage is the primary input rather than current. Choose the approach that matches which value you know first.

What resistance gives 80 ohms at 120 volts?

Resistance is fixed by the component, not the voltage. At 120 V, an 80 Ω resistor draws I = V / R = 120 / 80 = 1.5 A and dissipates P = V² / R = 120² / 80 = 180 W. To get 80 Ω from this tool, enter 120 V with 1.5 A (R = 120 / 1.5 = 80 Ω).

Volts to Ohms Calculator

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

Convert voltage to resistance in ohms using Ohm's Law (R = V / I) or the power formula (R = V² / P).

Enter Values

Voltage (V) *

Calculate using

Current (A)

Enter voltage and current or power, then click Calculate.

Resistance

0 Ω

Formula Applied

Parameter	Value

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Summary

Convert voltage to resistance in ohms using Ohm's Law (R = V / I) or the power formula (R = V² / P).

How it works

Select whether you know the current (A) or the power (W).
Enter the voltage in volts (V).
Enter either the current in amperes or the power in watts.
Click Calculate to apply Ohm's Law (R = V / I) or the power formula (R = V² / P).
The result shows resistance in ohms along with the full formula breakdown.
Copy the result for use in documentation or further calculations.

Use cases

Calculate the resistance of a circuit element given its supply voltage and operating current.
Determine resistance from voltage and power ratings on a component datasheet.
Size a current-limiting resistor for an LED or other low-power device.
Verify that a heating element's resistance matches its rated voltage and power.
Troubleshoot electrical circuits by comparing calculated resistance to measured values.
Convert voltage and current readings from a multimeter into resistance.

Frequently Asked Questions

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