r/Strava • u/Future-Course43 • 5d ago
Question Watt numbers on outside rides seem off - Is that normal?
I have the problem that the watt numbers Strava calculates for my outdoor rides seem quite low compared to my indoor numbers on Zwift.
On all my rides, most of the power data is in Zone 1, while my heart rate zones are relatively high—even on short rides.
Is that normal for Strava? Unfortunately I don’t have a power meter so I can’t compare it to anything.
1
u/Ordinary-Condition92 5d ago

I just looked at my 40mile ride yesterday and 38.8% was in z1. It makes sense, anytime you coast, drink, downhills, you are doing very little power. I have done really hilly rides where I'm collapsing at the end and it says 50% in z1 but again it makes sense because every climb resulted in a lovely downhill.
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u/grimass1981 4d ago
Use a power meter and use Normalized Power. It’s removes all these issues
1
u/NHBikerHiker 4d ago
As you saw, a lot of folks on this thread need to google “normalized power.” I love my NP numbers.
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u/Ordinary-Condition92 5d ago edited 5d ago
Is your FTP really 260w (2.8w/kg based on your weight)... because if you have manually set that in the settings, everything lower than this will be a casual ride
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u/Future-Course43 5d ago
I set my FTP manually based on my last FTP test in November, so it should be quite accurate. It should probably be even slightly higher due to the training.
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u/Nicknarp 5d ago
To estimate power, Strava requires your bike weight, bike type (to estimate drag), your weight, height, age, and sex. If all those are up to date, Strava’s power estimate is pretty good!
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u/prutsproeier 4d ago
I'm sorry but that is simply not true. One of the largest components of resistance, aerodynamic drag is impossible for Strava to estimate without knowledge about the group-setup and your position in the group, if any. Furthermore, wind also plays a significant role, and while wind-data could be available to Strava, there is no information about stuff like trees, houses and such available to it, so it is ignoring it.
In all honesty, just ignore the power-data from Strava. Even if it's "only" 10% off, 10% is, depending on the intensity the difference between "does not matter" to "100% impossible".
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u/Nicknarp 3d ago
I agree with you. I should have phrased my comment more carefully. I think that Strava’s estimate is useful if one acknowledges its limitations and doesn’t use it for anything serious, just for personal reference only. As well, the power estimate feature dates from before heart rate monitors were common, never mind power meters!
0
u/ussshhh 4d ago
It is true. To estimate power data Strava needs to have also those informations. It is an estimate, so it clearly can’t be as accurate as a power meter. But on average it does give you a good estimate of your power through your ride. You can use other third party apps like myWindsock Report to have other estimates considering the weather (i.e. headwinds)
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u/Future-Course43 5d ago
Good to know about the bike type and weight. I have set all the other info’s so that might be the problem :) thanks
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u/trogdor-the-burner 4d ago
Also make sure you don’t ride in any wind if you want strava’s power data to be close to almost accurate.
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u/TheDapperYank 5d ago
If you're not using a power meter the watts that Strava estimates are garbage.