Ohm's law calculator
Ohm's law ties three quantities together: voltage equals current times resistance. Any two of them give the third, and a fourth — power — follows from voltage times current.
V
Ω
Current
2.3A
- Power
- 529W
Rates and thresholds
- Voltage
- U = I × R
- Current
- I = U ÷ R
- Resistance
- R = U ÷ I
- Power
- P = U × I
How do I use Ohm's law?
Pick the form where the unknown stands alone on one side. With 12 volts across 4 ohms, the current is 12 ÷ 4 = 3 amperes, and that circuit's power is 12 × 3 = 36 watts. Three quantities and four formulas cover every combination.
How much current does a 2000-watt appliance draw?
Divide power by voltage: at Estonia's 230-volt mains, a 2000-watt appliance draws 2000 ÷ 230 ≈ 8.7 amperes. A typical household breaker is rated 16 amperes, so two such appliances on one circuit are already at the limit and a third will trip it.
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