More watts indoors= more speed outdoors?

Just curious to know if your FTP was 200watts and in 6 weeks you had a 10% increase to 220watts does that also mean a similar gain in your speed outdoors?

To oversimplify, yes. You will go faster.

However, you will not be 10% faster because the nature of wind resistance, road grade, power production and such are non-linear relationships. So, don’t expect that a 10% increase in FTP means you will increase from 20 mph avg to 22 mph avg. The end result is far from simple like that.

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To add to Chad’s answer, wind resistance increases with the CUBE of your speed. Going twice as fast requires 8 times the watts to overcome air resistance.

On a steep hills, 10% more watts will give you close to 10% more speed, but on the flats you can expect only a slight increase in speed.


Loosely yes but pacing (where you apply that power) in addition to drag, wind, rolling resistance etc will determine your speed change.

Interesting… seems about right since I’ve gained a lot of watts, but my strava segment improvements can be measured in 10-15 s blocks at a time, but when I get on my mountain bike, I can sometimes crush my old PR by a minute or more.