The Ohm's law triangle
An easy way of remembering the formula is to use the Ohm's law triangle. The application shown represents the use of the Ohm's law triangle as follows.
To help you remember the formula, draw an Ohm's law triangle. Then, place your thumb over the unit you wish to determine. The appropriate formula is shown as follows:
If you cover V for voltage then the the formula is IR
V = I x R
If you cover I for current then the the formula is V over R
I = V / R
If you cover R for resistance then the the formula is V over I
R = V / I
If any two values in a circuit are known, the third value can be calculated.