@Lémonsqueezer buy/borrow a garmin with a cadence sensor for a while and reep the datas.
This linked ride is on a freewheel 46/18 and commuting in the wet+dark so my speed is up down up down as I stop for lights and stuff but it gives you exact numbers with a map and everything once you shove it into garmin connect/strava/whatever, especially with cadence it's all just guessing until you use magnets. Seems I averaged 74 and apart from the sensor mess up peaked at 140ish for a few bits but most of it seems to be in the 90s when you hover over it until I got back over the river on the way home and was chilling.
If you're riding fg/ss then you can calculate it from your speed.
If you're riding geared you can count a foot against 30s on a watch (then double it obvs). Do this for a few weeks and it becomes pretty easy to judge within 5rpm.
@Lémonsqueezer buy/borrow a garmin with a cadence sensor for a while and reep the datas.
This linked ride is on a freewheel 46/18 and commuting in the wet+dark so my speed is up down up down as I stop for lights and stuff but it gives you exact numbers with a map and everything once you shove it into garmin connect/strava/whatever, especially with cadence it's all just guessing until you use magnets. Seems I averaged 74 and apart from the sensor mess up peaked at 140ish for a few bits but most of it seems to be in the 90s when you hover over it until I got back over the river on the way home and was chilling.
http://www.strava.com/activities/217902246/analysis