How to run a 20 minute FTP test
Pace, warm up and pick a course for a clean 20 minute power test, then turn the average into an accurate FTP.
Why the 20 minute test exists
The purest FTP test is a full hour at maximum sustainable power, but almost nobody can pace or stomach that. The 20 minute test is the practical stand-in: ride all-out for 20 minutes, then trim 5 percent off the average to approximate the hour you did not have to suffer through. That single adjustment is why a 250 watt 20 minute effort becomes a 237.5 watt FTP.
Warming up so the test counts
Cold legs produce a false low number, so build in before the effort. A common routine is ten easy minutes, a few short high-cadence bursts, and a hard five minute opener to clear the initial fatigue that would otherwise drag down your 20 minute average. Recover for several easy minutes after the opener, then start the test fresh so the whole 20 minutes reflects true threshold power.
Pacing the 20 minutes
The classic mistake is starting too hard and fading, which lowers your average and understates FTP. Aim for an even effort you could just barely hold to the final minute, then lift the pace in the last two or three minutes if anything is left. A flat road, a long steady climb or an indoor trainer all work, because steady terrain makes even pacing far easier than a route full of corners and descents.
Turning the average into training zones
Once you have the 20 minute average, this calculator applies the 95 percent factor and lays out all seven Coggan zones in watts. Endurance rides then sit in Zone 2, sweet-spot and threshold work near Zone 4, and short intervals push into Zones 5 and 6. Retest on the same course after a training block to see whether the whole set of zones has shifted up.