Cycle Trainer Distance Display

Hi there,
My first post regarding Arduino.
I'm a member of staff at an Air Cadet squadron - and looking to do project to build a distance display to work with a bicycle turbo trainer.
I have seen pieces on rev counters (tachometer), but wanted a rev counter that could be used with the wheel circumference to calculate distance travelled.

Any thoughts

John B

If you know wheel circumference you can use a single Hall-effect sensor and a magnet to detect rotations:

distTraveled = numRotations x wheelCircumference;