Strava vs PowerTap

Hello guys, so, heres my story/question

I have an Elite Drivo and a Tacx Neo. I’ve done FF with both trainers and get an FTP of 193 and 195.
seems pretty constant and all ok.

Now, lets go ride outside.
There is a very famous segment in my city that I can complete in about 22mins. so its perfect to do an outside ftp test. right?
I’ve done it several several times using a Powertap G3 powermeter, and Wahoo Bolt.
I finish it with an average power of 240W
I’ve read that you can produce more Watts outside than inside, so I was OK with these results for about a year.

2 weeks ago, I forgot to check the batteries of the G3, and it was dead… So I simply went to ride, do my segment as ussual, and keep having fun.

When checking on strava, I did a PR!!! but my estimated power (I have my correct weight and bikes weight) was 197W!! pretty similar to what FF says!!!

now I dont know what to believe… Is the Strava estimation better than the actual power meter I use?

Any ideas? …

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What was the wind direction? If your 240w efforts were into a headwind that could be why. Otherwise might be worth watching this


Hi there.

Personally I’d ignore Strava’s estimated power value. I have looked at some of these in the past and thought they bear less resemblance to what I consider reality.

You have an indoor number which is spot on. That’s the one you pretty much use for training if using structure platforms and plans I guess - so that is the thing that will ultimately help you improve, as your workouts will be based on that (typically).

You possibly have an outdoor number from your pedals that is ‘informative’ if you’re trying to compare outcomes of your training while outdoors. I’d treat that number as ‘interesting’ as well but not relate it to your indoor training stats.

All in all sounds like things are going great !!

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Awsome replies guys. thanx.
Sir_Martin, I think knowing your outside numbers are super important so you can pace yourself. its a shame they dont match so you could simply use the “holly grail” indoor numbers. I also feel the ones you get from your trainer are super important… but just for training.

Alistair_Brown. THANX a lot for that video. It solved my question 100%
I went to that website, and entered the values for the segment I was talking about.
The results are always 1-2% off from the PowerMeter. Even when I did the PR without the PowerMeter, I got a result pretty similar to what I would have gotten! That been said,

Dont trust Strava estimates!!! :slight_smile:

Happier now knowing im stronger than what strava thinks :wink:


Strava is, typically, fairly accurate though, so long as you’ve put in the correct data in the first place.
Is your profile up to date with your weight and the weight of the bike you’re using? If you’ve not got that data in Strava then it hasn’t got the faintest clue where to start it’s calculation…

(Just playing Devil’s advocate on behalf of that company :slight_smile: )


Hello Jon,
yes. I keep the profile super updated.
I did what Alistair_Brown suggested in the video, and it matches very accurate with the powermeter.

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Strava is normally fairly solid in its estimations (I imagine it uses a formula similar to that on the video), but it does try to use weather data, maybe its wind data was wonky for the time period.

DC Rainmaker reckons Strava is close enough for the average person to take pause over purchasing power meters and he’s someone I would typically listen to on such things.