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⚡ Ohm's Law Calculator

Enter any 2 values to calculate voltage, current, resistance, and power instantly.

V = I × R  |  P = V × I

📊 Power Formulas Reference

P = V × I
Power from Voltage & Current
P = I² × R
Power from Current & Resistance
P = V² / R
Power from Voltage & Resistance

📋 Electrical Reference Table

Common Voltage Levels

SourceVoltageType
AA/AAA Battery1.5VDC
USB Port5VDC
Car Battery12VDC
USB-C PD20VDC
US Household120VAC
EU/UK Household230VAC
US Industrial277V / 480VAC
High Voltage Line110kV–765kVAC

Standard Resistor Values (E24)

ResistanceAt 5VAt 12VPower (at 12V)
10 Ω0.5 A1.2 A14.4 W
100 Ω0.05 A0.12 A1.44 W
220 Ω0.023 A0.055 A0.655 W
470 Ω0.011 A0.026 A0.306 W
1 kΩ0.005 A0.012 A0.144 W
4.7 kΩ0.001 A0.003 A0.031 W
10 kΩ0.0005 A0.001 A0.014 W

📋 How to Use

  1. Enter any two known values (voltage, current, resistance, or power) into the input fields.
  2. The calculator automatically computes the remaining two values in real time.
  3. Review the formula box to see which equations were used for the calculation.
  4. Use the power formulas reference for quick lookups of common calculations.
  5. Check the electrical reference tables for common voltage levels and resistor values.

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❓ Frequently Asked Questions