Ohm’s Law Calculator

Calculate Voltage (V), Current (A), Resistance (Ω), and Power (W) with unit conversion

V
A
Ω
W

Voltage (V): -
Current (I): -
Resistance (R): -
Power (P): -

Tool Instructions & Shortcuts

How to Use:

  • Enter exactly 2 known values from Voltage (V), Current (I), Resistance (R), or Power (P).
  • Use decimal points for precision (e.g., 12.5, 0.001) - only numbers and decimals are accepted.
  • Click the up/down arrows next to each field to change units (mV, kV, mA, kΩ, etc.).
  • Once 2 fields are filled, remaining fields are automatically disabled to prevent conflicts.
  • Click "Calculate" or press Alt + Enter to compute missing values.
  • Results show all 4 values with the formula used displayed above.
  • Click "Clear" or press Alt + C to reset all fields for new calculations.

Supported Calculations:

  • Basic Ohm's Law: V = I × R, I = V ÷ R, R = V ÷ I
  • Power Formulas: P = V × I, P = V² ÷ R, P = I² × R
  • Derived Equations: V = P ÷ I, I = P ÷ V, R = P ÷ I², etc.

Available Units:

  • Voltage: nV, µV, mV, V, kV, MV, GV
  • Current: nA, µA, mA, A, kA, MA, GA
  • Resistance: nΩ, µΩ, mΩ, Ω, kΩ, MΩ, GΩ
  • Power: nW, µW, mW, W, kW, MW, GW, hp

Keyboard Shortcuts:

  • Alt + Enter: Calculate results from entered values.
  • Alt + C: Clear all input fields and results.
  • Tab / Shift + Tab: Navigate between input fields and controls.
  • Click input field: Select all text for easy editing.

Usage Tips:

  • Smart Input: Enter your 2 most accurate known measurements first.
  • Unit Selection: Choose units that give numbers between 0.001 and 999,999 for best readability.
  • Applications: Circuit design, power analysis, safety calculations, and troubleshooting.
  • Limitations: Designed for DC circuits with resistive loads under ideal conditions.

Note: Always verify calculations before building circuits. Consider component ratings and safety margins for practical applications.