I recently picked up a powertap and have done a fair bit of riding around and a few races now with it on, so I've started to get familiar with some of the numbers. I would like to figure out what my functional threshold power (FTP) is and would like to know which methods are more accurate.

I know a 40km time trial is sort of the gold standard, but I find these so mentally tough that it's nearly impossible for me to give an honest effort outside of a race situation.

Nothing is going to be easy, I imagine as any interpolated ways of doing this will probably require maximum effort for a certain amount of time, but I'm hoping there is a reasonably accurate method that is easier mentally and physically.

5 Answers 5


First, get 'Training and Racing w/ a Power Meter' by Hunter Allen and Andrew Coggan. So incredibly helpful in learning about your device. Second, use WKO+ for analysis. I have been using it for 4 years and it is fantastic.

In reference to you question, I typically use the 20 min time trial as a good way of setting my training zones. After a solid warm up (typically with a 5 min LT--->V02 effort) and then proper rest I do a flat 20 min TT. I take the avg. power from that TT (not the norm. power) and multiply by .95 (or take 5% off, whatever is easiest). For example: a 300 watt average over 20 mins would indicate an FTP of 285.

What I do after that is keep an eye on my IF (intensity factor) and my TSS (training stress score). If that is all gibberish to you I would recommend getting the book!




Joe Friel claims a 30-minute TT which is not part of a race (ie, when the athlete is less motivated) estimates FTP. He also suggests FTP can be estimated from weight and age, though clearly this is only going to hold for athletes who are similarly trained. Other estimations of FTP include the NP from a hard 1 hour mass start race.

See this 7 deadly sins article for more.


There are lots of different field tests approaches. I've been using the Carmichael one (two 9-minute full out TTs with a cooldown between them).

  • That's similar to what I was instructed by them (2006), 2 x 3 mile max effort or 8 minutes on trainer. I wonder if it's been changed? I think they increase that for advanced athletes who have very consistent time between the two.
    – imel96
    Nov 27, 2013 at 5:51
  • They did change from 2x3 miles to 2x9 minutes. Carmichael talks about in the time crunched cyclist Dec 20, 2013 at 3:26

You might interest a friend of similar skill in a 40km time trial? You could both work on beating the other which might help you with the mental toughness outside of a race.


I wrote a quick guide outline some of the best and effective testing methods you can use. These are word for word how they are delivered to my own athletes. Enjoy!

How to find your functional threshold

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