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Ohms Law Calculator

The three calculators below calculate voltage, current or resistance using ohms law. Fill in the two boxes on the left and the missing vlaue will be calculated and shown on the right. The resistance calculator also shows preferred resistor values; use the radio buttons on the calculator to select the preferred value series to use.

Voltage Calculator (V = I * R):

Voltage = ?

Current Calculator (I = V / R):

Current = ?

Resistance Calculator (R = V / I):

E12 E24 E48 E96 E192
Resistance = ?
Preferred Resistance = ?


The formula for Ohms Law is:

V = I * R, where V is voltage, I is current and R is resistance

This can be re-arranged to find current or resistance:

I = V / R
R = V / I

For more details of Ohms Law, and the 'Ohms Law triangle' (an easy way to remember and re-arrange the formaula) click here.

If you found this calulator useful you should try Electronics Assistant!

Electronics Assistant
  • All the online calculators and more in a stand-alone application
  • Converts Resistor & Inductor colour codes, calculates LED series resistors, capacitance units, series / parallel resistors & capacitors, frequency, reactance & more
  • Calculation of nearest preferred resistor values with a choice of 5 series from E12 to E192
  • Print & save calculation results