What is the formula for ohms to volts?

Using Ohm's Law: V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. If you know power instead of current, use V = √(P × R), where P is power in watts.

Does this work for AC circuits?

Yes, for purely resistive AC loads (e.g. resistors, incandescent bulbs, heating elements) both formulas apply directly. For reactive loads with inductors or capacitors, use impedance (Z) in place of resistance (R) — the arithmetic is identical.

What units should I enter?

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

Why does the result show a dash instead of a number?

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

What is the difference between the two formulas?

Use V = I × R (Ohm's Law) when you know the current flowing through the resistor. Use V = √(P × R) when you know the power dissipated by the resistor but not the current.

Ohms to Volts Calculator

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

Calculate voltage from resistance and current using Ohm's Law (V = I × R), or from resistance and power (V = √(P × R)).

Formula

Resistance (R)

Current (I)

Enter resistance and current (or power) to calculate voltage

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Summary

Calculate voltage from resistance and current using Ohm's Law (V = I × R), or from resistance and power (V = √(P × R)).

How it works

Choose your known values: current (amps) or power (watts).
Enter resistance in ohms (Ω) in the Resistance field.
Enter the second known value — current in amps or power in watts.
Voltage is calculated instantly and displayed in volts.
Use the Copy Result button to copy the output to your clipboard.
Click Reset to clear all fields and start a new calculation.

Use cases

Find the voltage across a resistor when current and resistance are known.
Calculate supply voltage requirements from power consumption and load resistance.
Verify circuit designs before prototyping or purchasing components.
Cross-check electrical datasheets and spec sheets for accuracy.
Convert ohms and amps to volts for motor, heater, or LED driver circuits.
Solve homework and exam problems involving Ohm's Law.

Frequently Asked Questions

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