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Electrical Power Calculator

Solve any two of V, I, R, P for the rest.

Introduction

Electrical Power Calculator — Solve any two of V, I, R, P for the rest. Enter Voltage (V) — leave blank if unknown, Current (A) — leave blank if unknown, Resistance (Ω) — leave blank if unknown, Power (W) — leave blank if unknown to get an instant, accurate result.

Formula

Electrical power can be calculated three equivalent ways depending on known values: P = V × I, P = I² × R, or P = V² / R, where V is voltage, I is current, and R is resistance. Enter any two known values to solve for the rest.

Step-by-step

  1. Enter the Voltage (V) — leave blank if unknown.
  2. Enter the Current (A) — leave blank if unknown.
  3. Enter the Resistance (Ω) — leave blank if unknown.
  4. Enter the Power (W) — leave blank if unknown.
  5. Click Calculate to see your result instantly.

Real-world example

Example: With Voltage (V) — leave blank if unknown = 12, Current (A) — leave blank if unknown = 2, the Electrical Power Calculator gives V: 12, I: 2, R: 6.

Frequently Asked Questions

Why are there multiple formulas for electrical power?
All three formulas derive from combining the power equation (P = VI) with Ohm's Law (V = IR), giving equivalent expressions depending on which two of voltage, current, and resistance you know.
What units does this calculator use?
Enter values in volts (V), amperes (A), and ohms (Ω) as available, to get power in watts (W).
How is electrical power related to energy bills?
Power (in watts) measures instantaneous energy use, while energy consumption over time (used for billing) is power multiplied by time, typically expressed in kilowatt-hours (kWh) — see the electric energy calculator.
What inputs does the Electrical Power Calculator need?
You'll need to provide: Voltage (V) — leave blank if unknown, Current (A) — leave blank if unknown, Resistance (Ω) — leave blank if unknown, Power (W) — leave blank if unknown. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Electrical Power Calculator?
The Electrical Power Calculator applies the formula exactly as calculated — Electrical power can be calculated three equivalent ways depending on known values: P = V × I, P = I² × R, or P = V² / R, where V is voltage, I is current, and R is resistance. Enter any two known values to solve for the rest. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Electrical Power Calculator free to use?
Yes, the Electrical Power Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Electrical Power Calculator

The Electrical Power Calculator uses a real, verifiable formula — Electrical power can be calculated three equivalent ways depending on known values: P = V × I, P = I² × R, or P = V² / R, where V is voltage, I is current, and R is resistance. Enter any two known values to solve for the rest. — so results are accurate every time, not an approximation.