Utilnaro

Electricity and circuits

Ohm's law

Calculate voltage, current, or resistance for an ohmic component using compatible electrical units.

Formula

U=IR U = I × R

For an ohmic component under stable physical conditions, voltage equals current multiplied by resistance.

Ohm's law calculator

What do you want to calculate?

Known values

The result updates automatically.

Result

12 V

Substitution and calculation

U = I × R = 2 A × 6 Ω = 12 V

Symbols and units

SymbolQuantitySISupported units
UvoltagePotential difference across the component.VV, mV, kV
Ielectric currentRate of electric charge flow through the component.AA, mA
RresistanceOpposition of the component to electric current.ΩΩ, kΩ, MΩ

Formula rearrangements

Calculate voltage

U = I × R

Calculate current

I = U / R

Calculate resistance

R = U / I

Worked examples

Current through a resistor

A 6 Ω resistor has 12 V across it. Calculate the current.

  1. 1Step 1: Use I = U / R.
  2. 2Step 2: Substitute U = 12 V and R = 6 Ω.
  3. 3Step 3: Divide to obtain 2 A.

Result: 2 A

Resistance from voltage and current

A device draws 0.5 A at 230 V. Calculate its resistance in this operating state.

  1. 1Step 1: Use R = U / I.
  2. 2Step 2: Substitute U = 230 V and I = 0.5 A.
  3. 3Step 3: Divide to obtain 460 Ω.

Result: 460 Ω

Sources and review