Why your Strava (or Garmin) elevation gain doesn't match
Same ride, three apps, three elevation gains. It isn't a bug: each tool measures altitude differently and processes it differently before adding up the climbs.
By Thomas, road and gravel rider · published November 7, 2026
Where the altitude comes from
- A barometer. Many bike computers and watches measure air pressure and work altitude out from it. It tracks changes well, but pressure also moves with the weather: a front passing during a long ride shifts the reading.
- GPS only. A phone or a unit without a barometer gets altitude from the satellites, which is much less precise vertically than horizontally. The altitude wobbles by a few metres from point to point, and those wobbles end up counted as climbing.
- A terrain model. For a route drawn on a map, or when asked to, the platform gives each point the altitude of a digital elevation model. The result depends on how detailed the model is: a bridge or a tunnel can show up as a valley or a hill.
What each app does with it
Several services can replace recorded altitudes with those from a terrain model. Strava and Garmin Connect offer this kind of correction in some cases; whether it's applied or not changes the total for the same ride. Then each tool smooths the altitude more or less heavily before adding up the climbs: heavy smoothing irons out short kicks, light smoothing counts noise as climbing. Finally, the number of points in the file matters: the fewer there are, the more small bumps disappear.
A measured example
On my 281 km ride of 1 November, Strava shows 2,070 m of climbing. With only 600 altitude points spread over the route, the raw sum drops to 1,651 m: the bumps between two points have gone. On a test route with a few metres of noise around a known 800 m climb, the raw sum went over 1,500 m, and this site's smoothed calculation gave 789 m.
What to do
- To compare two rides, use the same tool for both.
- When preparing an event, treat the organiser's figure as a ballpark, not a number accurate to the metre.
- To see what your file gives, drop it into the GPX elevation gain calculator: it shows raw and smoothed gain side by side.
For more on reading gradients, the guide on how to read an elevation profile takes over, and the tool to create an elevation profile from GPX turns your route into an image.
Frequently asked questions
Does Strava overestimate elevation gain?
Not always: depending on the altitude source and the correction applied, its number can be higher or lower than another tool's. There's no single exact value.
Should I turn on elevation correction?
It mainly helps when the recorded altitude is noisy (GPS without a barometer). To compare rides, keep the same setting.
Why does the gain change after I upload a file?
The platform receiving the file often recalculates the total with its own smoothing, or even its own altitudes.