How to find RPM of a spinning robot

I am trying to find the RPM of my 2 motor robot as it spins in circles. Does anyone know how I could use the inertial sensor on the EXP brain for this? I am trying to make a translational drift robot. Just to clarify, this is not for competition. Also, could we get a programming category?

Because RPM is a measure of rotations per minute, you can find you robot’s RPM by dividing how many times you have rotated over a certain amount of time by that amount of time in minutes to get your average RPM over that amount of time.