I finally got to test my best 20 minute average power today to estimate my FTP. However, I found another FTP estimation method online other than the one I already knew, which was 95% of 20 min average power.

The other method is the following. Quoting source from power2max website https://www.power2max.com/northameri...culate-my-ftp/

Estimating from short duration tests

If you have a recent 5 and 20-minute best effort, you can estimate your FTP. Some sources suggest that simply taking 95% of your 20 minute value offers a reasonable estimate. I have found that this significantly over-estimates the FTP in most circumstances and offer this alternative method:

Identify the % drop off from your 5 to 20 minute test
e.g. if 5 minute = 400W & 20minute = 300W, the drop is 100W or in % terms, 100/400 = 25%.

2. Multiply this % by 0.75 = 18.75%

3. Take this % off the athlete’s 20 minute value to get a good estimate of FTP.

So, for this athlete, we would multiply his 20 min test of 300W by 18.75% = 56W and subtract this from 300W to get a good estimate of FTP, in this case, 244W.

This method takes into account the very real differences in each athlete’s power-duration or ‘fatigue’ curve, a concept we’ll explore in future articles.


I'm a recreational cyclist starting to learn about power training trying to improve. In your experiences, which method is more accurate? Intuitively, the second method makes more sense to me as it attempts to take into consideration the "fatigue profile" of an individual athlete rather than assuming a flat 5% decline for everybody. I'm wondering if I should test my 5 min max power as well. I've looked at a lot of numbers for the past couple of weeks from Strava Premium power curve, WKO4 free trial, TrainingPeaks and Golden Cheetah. I'm starting to think the only way to really get my true FTP is to actually do a 60 minute max power run which would be painful to do.