How to read an elevation profile without getting caught out

Trap one: the vertical scale

On almost every profile, the vertical axis is exaggerated compared with the horizontal one. In the image above, the ride is 281 km long and the altitude ranges from about twenty metres to 155 m. With both axes at the same scale, the profile would be a flat line. That helps you see the bumps, but it's misleading: two profiles that look alike on screen can feel nothing alike on the bike.

Always read the scale. A bump that fills half the height of the image might be 50 m of climbing on a flat route or 1,500 m on an alpine one. The stickers and images on this site adapt the vertical scale to your route automatically: compare the numbers, not the shapes.

Working out a gradient

A gradient is the height gained divided by the distance covered, times 100. A road that climbs 100 m over 1 km is at 10%. A 300 m climb over 5 km averages 6%.

The key word is “average”. A 5 km climb at 6% can be steady, or hide a flat bit followed by a much steeper ramp. On a profile, look for where the line kicks up: that's where it hurts, not necessarily where the total climbing is highest. Climb profiles published by clubs and specialist sites often split the climb into one-kilometre sections with the gradient of each: that's the most useful way to read it for pacing.

What elevation gain really measures

Elevation gain is the sum of every climb on the route, big and small. A route that climbs 50 m, drops 50 m and climbs another 50 m totals 100 m of gain, even if it finishes at the same altitude it started.

Because it adds everything up, elevation gain is very sensitive to small variations. If the recorded altitude wobbles by a metre or two at every point because of measurement noise, those wobbles add up over thousands of points and inflate the total. Conversely, if the file has few points, the small bumps between two points disappear and the total drops.

Why Strava, Garmin and Komoot don't agree

There isn't one “true” elevation gain for a ride: there are different ways of measuring it, and each gives its own number.

• Where the altitude comes from. A unit with a barometer measures air pressure, which shifts with the weather. A phone or a unit without a barometer works altitude out from GPS, which is far less precise vertically. And a route drawn on a map gets its altitudes from a terrain model.
• Corrections. 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 on or not changes the number.
• Smoothing. Before adding up the climbs, every tool irons out small variations to a greater or lesser extent. Heavy smoothing underestimates short kicks; light smoothing counts noise as climbing.
• The number of points. The same ride exported with one point per second or one point every few hundred metres won't give the same total.

A real example with my 281 km ride: Strava shows 2,070 m of climbing. With only 600 altitude points spread over the route, about one every 470 m, the raw sum of the climbs drops to 1,651 m. The small bumps between two points have gone. That's why, on this site's examples, I show the elevation gain Strava calculated from the full recording.

When you import a route on this site, the tool resamples the altitude every 25 m, then smooths it over about 200 m before adding up the climbs. On a test route where I added a few metres of artificial noise to a known 800 m climb, the raw sum went over 1,500 m, and the smoothed calculation came back to 789 m. So the number shown can differ by a few percent from your app's, and that's normal.

Spotting the sections that matter

When I prepare a ride, I read the profile in this order:

1. The long climbs: their length, average gradient and position. A 10 km climb at kilometre 200 isn't paced like one at kilometre 20.
2. The steep bits: where the line rears up sharply, even over a short distance. On gravel with loose ground, those are the ones that can make you walk.
3. The sequences: a string of short climbs with no real recovery is sometimes more tiring than a single long climb, and it's where the elevation gain piles up without you noticing.
4. The descents: on a long ride, a big descent at dusk or on a broken track deserves as much attention as a climb.

Once you've spotted them, put them where you'll see them: as markers in the elevation profile generator, or as climbs on your race profile sticker. And to match the hard sections with water stops, the guide to planning your feed stops takes over.