# Ohm's Law Calculator (V = IR)

Free Ohm's Law calculator. Solve for voltage, current, or resistance using V = IR. Also calculates power. Essential tool for electronics and electrical.

## What this calculates

Ohm's Law defines the fundamental relationship between voltage, current, and resistance in an electrical circuit: V = IR. Named after German physicist Georg Simon Ohm, this law is the cornerstone of circuit analysis and electrical engineering. This calculator lets you solve for any one of the three variables and also computes the power dissipated.

## Inputs

- **Solve For** — options: Voltage (V), Current (I), Resistance (R)
- **Voltage** (V) — min 0
- **Current** (A) — min 0
- **Resistance** (Ω) — min 0

## Outputs

- **Result** — Calculated value for the selected variable
- **Unit** — formatted as text
- **Power** (W) — Electrical power dissipated (P = IV)
- **Formula Used** — formatted as text

## Details

Ohm's Law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with the constant of proportionality being the resistance (R):

  - V = I × R — Voltage equals current times resistance

  - I = V / R — Current equals voltage divided by resistance

  - R = V / I — Resistance equals voltage divided by current

The calculator also computes electrical power using P = IV, which tells you how much energy the circuit dissipates per second (measured in Watts).

Units: Voltage is in Volts (V), current in Amperes (A), resistance in Ohms (Ω), and power in Watts (W). Ohm's Law applies to ohmic (linear) materials where resistance remains constant regardless of applied voltage.

## Frequently Asked Questions

**Q: What is Ohm's Law?**

A: Ohm's Law states that voltage (V) equals current (I) multiplied by resistance (R): V = IR. It describes how electrical potential, current flow, and resistance relate in a circuit.

**Q: What are the units used in Ohm's Law?**

A: Voltage is measured in Volts (V), current in Amperes or Amps (A), and resistance in Ohms (Ω). Power derived from Ohm's Law is measured in Watts (W).

**Q: Does Ohm's Law apply to all materials?**

A: Ohm's Law applies perfectly to ohmic materials (like most metals at constant temperature) where resistance is constant. Non-ohmic materials (like diodes, transistors, and thermistors) do not obey Ohm's Law because their resistance changes with voltage or current.

**Q: How is power related to Ohm's Law?**

A: Power (P) = IV. Combined with Ohm's Law, you get P = I²R and P = V²/R. These allow you to calculate power using any two of the three electrical quantities.

**Q: What happens if resistance is zero?**

A: A resistance of zero means a short circuit. Theoretically, infinite current would flow for any applied voltage. In practice, the wire or source has some internal resistance, and a short circuit can cause dangerous overheating or blow a fuse.

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Source: https://vastcalc.com/calculators/technology/ohms-law
Category: Technology
Last updated: 2026-04-21