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Ohm's Law & Electrical Power Calculator

Calculate V = I × R voltage, current, resistance, and electrical power.

Last reviewed by the myCalculator Editorial Team

Input Parameters

Calculation Results

Current (I = V / R)
3Amperes (A)
Electrical Power (P = V × I)
36Watts (W)
Voltage (V)
12Volts (V)
Resistance (R)
4Ohms (Ω)
Step-by-Step Calculation Solution
1.Ohm's Law: V = I × R
2.Current I = V / R = 12 / 4 = 3 A
3.Power P = V × I = 12 × 3 = 36 W

Formula & How Ohm's Law & Electrical Power Calculator Works

Mathematical Formula
V = I × R, P = V × I

Ohm's law links voltage, current and resistance: V = I × R. Power is P = V × I. A 12 V supply across a 6 Ω resistor drives I = 12 ÷ 6 = 2 A, and the power is 12 × 2 = 24 W. Rearranged, R = V ÷ I and I = V ÷ R. You can also write power as I²R or V²÷R. Use the law to size resistors for LEDs, to check the current drawn by a load, or to work out whether a cable or fuse is adequate. Real components change resistance with temperature, so the law is most accurate for resistive loads at a steady temperature.

How to Calculate Ohm's Law & Electrical Power Calculator (Step-by-Step)
  1. Enter Voltage (V): Input your target parameter value.
  2. Enter Resistance (Ω): Input your target parameter value.
  3. Apply Formula: Calculate using V = I × R, P = V × I.
  4. Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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APA 7th Edition

MyCalculator.com.au. (2026). Ohm's Law & Electrical Power Calculator. Retrieved October 24, 2026, from https://www.mycalculator.com.au/calculators/physics/ohms-law

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MyCalculator.com.au. (2026) 'Ohm's Law & Electrical Power Calculator'. Available at: https://www.mycalculator.com.au/calculators/physics/ohms-law (Accessed: 24 October 2026).

Frequently Asked Questions (FAQs)

What is 1 Watt of electrical power?

1 Watt is 1 Volt producing a current flow of 1 Ampere.

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