Calculate U, R, I and P online

Online calculator for calculating voltage, current, resistance and power

Calculate Ohm's law and power online


To calculate the voltage U , the current I , the resistance R or the power P two of the values must be known.


Enter the two known values

Voltage U in volts
Current I in amperes
Resistance R in ohms
Leistung P in Watt

Decimal places



Ohm's law and power

Ohm's law is a basis of electrical engineering and electronics. It indicates the relationship between voltage, current and electrical resistance.

Calculate voltage

\(\displaystyle U=R · I\)
\(\displaystyle U=\sqrt{P · R}\)
\(\displaystyle U=\frac{P}{I}\)

Calculate current

\(\displaystyle I=\sqrt{\frac{P}{R}}\)
\(\displaystyle I=\frac{U}{R}\)
\(\displaystyle I=\frac{P}{U}\)

Calculate resistance

\(\displaystyle R=\frac{P}{I^2}\)
\(\displaystyle R=\frac{U^2}{P}\)
\(\displaystyle R=\frac{U}{I}\)

Calculate electrical power

\(\displaystyle P=U · I\)
\(\displaystyle P=I^2·R\)
\(\displaystyle P=\frac{U^2}{R}\)