I see lots of cadence-related questions on here where people cite fairly specific cadence rates. How do you calculate your cadence exactly? Do you just set a one-minute timer on your bike computer and count them manually?
If you don't have a cycling computer to do this for you, you can just count the top (or bottom) pedal strokes on one side for 15 secs and multiply the strokes by 4. That'll be your cadence. It's close enough for the casual cyclist.