Enter any 2 values and click 'Calculate'

Voltage (Volts):

Current (Amps):

Resistance (Ohms):

Ohm's Law is a fundamental formula in electronics. It explains the relationship between voltage, current and resistance. If you know any 2 of these values, you can work out the third using the formula:

V = I x R.

V is the voltage in Volts, I is the current in amps, and is the resistance in Ohms.

It's important to know Ohm's Law, but it can be difficult to remember, and difficult to calculate if they don't result in whole numbers. Our online Ohm's law calculator make it easy for you. Simply enter the 2 values you know, hit calculate, and the 3rd value will be automagically filled in for you!

Ohm's law is named in honour of the German physicist Georg Ohm. He was not the first to notice the correlation between resistance and current, but his paper published in 1827 was the first equation to fully explain the relationship between resistance, voltage and current, although his original law was more convoluted than than the one we have today. This law allows us to calculate any of the 3 values, using only 2 of the values. This, for instance, allows us to calculate the resistor needed in a circuit.