Outdoor vs indoor FTP

Hello all.
Today i ve done my 1st ride outdoor with a mtb powermeter. Until now i had done trainings indoor with a tacx neo and outdoor trying to follow RPE. Today i was going to perform the excercise i had planned for today (Carter), but instead of that, i did a 20’ ftp test to see if there was any difference between indoor and outdoor ftp. My surprise is that its a massive difference. My indoor ftp was calculated as 219 doing the ramp test, and outdoor today was 275 doing a 20’ test. So i would want to know what to do. Repeat the indoor test with a 20’ test? adjust outdoor excercises to outdoor ftp? keep for indoor excercises the outdoor ftp?

Thanks in advance

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ups, no reply?

Normally you will be have higher power outdoors as moving through the air and wind cools your body more, especially in the 20 min test.

Your numbers are 25% higher and that is way more than can be attributed to cooling. It seems something is off with your power meter or your trainer. Anytime there is a discrepancy of more than 5% you should investigate the equipment.

How far apart were your tests of 219 and 275? If they were months apart then you gained fitness and a lot of it. If they were close together, again, investigate.


Hi @Rc213v

I have pretty much the same β€œproblem”.

What did you do with these discrepancies? Do you use TR for outdoor workouts?


Assuming the 20’ minutes test outside was done correctly - and I have no doubt about that - and also assuming your powermeter worked correct: Yes, of course. Do your outside workouts based on the outside FTP. Absolutely. It’s absolutely no surprise (actually quite the norm as far as everything I gathered over the last years) to have a higher outdoor FTP than inside. The difference may vary. From person to person, from equipment to equipment and also from how used you are currently to indoor training (i.e. are you right at the end of a months long period where you had at least 2 indoor rides per week or did you do indoor rides only every now and then).

But for some or most - there will be a difference now matter how advanced your trainer model is and how often you are sitting on it.