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Tools / Ohm's law calculator (volts, amps, watts)

Ohm's law calculator: volts, amps, ohms & watts

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Result
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U = R × I, P = U × I = I² × R = U² ÷ R. For mains devices in Germany use 230 V (single-phase); for three-phase power the formula differs (√3 × 400 V × I × cos φ).

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How to use it

  1. Enter two known values (e.g. 2,000 W and 230 V).
  2. Leave the other two fields empty.
  3. Read all four values.
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Last checked: October 2026 · Based on: Ohm's law U = R × I; electric power P = U × I. Found a mistake? Use the form below – we fix confirmed errors and update the date.

Frequently asked questions

How many amps is 2,000 watts at 230 V?

I = P ÷ U = 2,000 ÷ 230 ≈ 8.7 A.

What does Ohm's law say?

Voltage equals resistance times current: U = R × I.

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