Cycling climb calculator
A climb’s gradient is height gained divided by distance: 700 m over 10 km is 7 %. How long it takes depends almost entirely on your power and total weight: at 250 W and 84 kg (rider and bike) that climb takes about 44 minutes, a VAM of about 950 m per hour. Enter any climb to get gradient, difficulty, time and VAM.
5 % more power saves 1:55; 2 kg lighter saves 0:55.
Same physics as the cycling speed calculator, hoods position, normal tyres, no wind. Fiets index = H² ÷ (D × 10) + (summit − 1,000) ÷ 1,000.
How the climb calculator works
Enter a climb's length, elevation gain and summit altitude, plus your power and weight, and the calculator gives you four things: the average gradient, a difficulty score, how long the climb takes you and your VAM. It is one of the free LeCoach cycling calculators.
- Gradient = elevation gain ÷ distance × 100.
- Difficulty uses the Fiets index: gain² ÷ (distance × 10) + (summit − 1,000) ÷ 1,000, with distance and heights in metres. The altitude part only counts above 1,000 m.
- Time comes from the same physics as the cycling speed calculator: gravity, rolling resistance and air drag, with you on the hoods, normal tyres and no wind.
- VAM is the height you gain per hour, in metres.
How hard is the climb?
The Fiets index, from the Dutch cycling magazine Fiets, rates a climb by how much it rises and how steep it is, with a little extra for high summits. Because gain is squared, a steep climb scores much higher than a long, gentle one with the same height.
| Fiets index | Difficulty |
|---|---|
| under 2 | Easy |
| 2–4 | Moderate |
| 4–6 | Hard |
| 6–8 | Very hard |
| over 8 | Legendary, for example Alpe d'Huez at about 9.1 |
The example climb, at 5.1, sits in the middle of the hard band. The index rates the climb, not you: how hard it feels depends on your power, weight and pacing.
Power and weight: what saves time
On a steep climb, most of your power goes into lifting you and the bike. Air drag matters little at 13 to 14 km/h, so your time depends almost entirely on watts per kilo.
For the example climb:
- 5 % more power (262.5 W instead of 250 W) saves 1:55, and you reach the top in 42:19.
- 2 kg lighter (82 kg instead of 84 kg in total) saves 0:55, and you reach the top in 43:20.
The 2 kg is about 2.4 % of the total weight, and it saves about half as much time as the 5 % power gain. Per percent, power and weight matter about equally on a climb like this. Remember that the weight that counts is everything: you, the bike, bottles and kit.
How time changes with power, same climb and weight:
| Power | Time | Speed | VAM |
|---|---|---|---|
| 200 W | 54:25 | 11.0 km/h | 772 m/h |
| 250 W | 44:15 | 13.6 km/h | 949 m/h |
| 300 W | 37:33 | 16.0 km/h | 1,118 m/h |
The watts per kg calculator shows how your power-to-weight compares with other riders, and our guide to power-to-weight ratio for cyclists explains how to improve it without losing power.
Want this worked out for you every day? LeCoach builds your training around your own numbers.
Try LeCoach for freeVAM explained
VAM (from the Italian velocità ascensionale media) is your average climbing speed in vertical metres per hour. Because it ignores length, it lets you compare your climbing on a 3 km hill with a 10 km mountain pass.
On steep climbs, VAM tracks your watts per kilo closely. On gentle gradients it reads lower at the same power, because more of your power goes into air drag and rolling resistance. Compare your VAM between climbs of a similar gradient.
Pacing a climb
- Start at a power you can hold to the top. Most riders go too hard in the first few minutes and lose more time later than they gained.
- Ride slightly harder on the steep parts and ease a little where it flattens. Steep sections are where your watts buy the most time.
- Plan for altitude. Above about 1,500 m, your sustainable power drops a little. On a long Alpine climb, start more conservatively.
- Gear for the slowest section. The bike gear ratio calculator shows what cadence your lowest gear gives at climbing speed.
For a structured approach, see our climbing training plan.
Common mistakes
- Entering only your body weight. Add the bike, bottles and kit. The calculator has a separate field for them.
- Using an optimistic power. Use the power you can actually hold for the time the climb takes, not your FTP if the climb takes much longer than an hour.
- Trusting the average gradient alone. A 7 % average with ramps of 12 % rides very differently from a steady 7 %.
- Mixing up summit altitude and elevation gain. Gain is what you climb; summit altitude is the height of the top above sea level.
When the numbers change
- Headwind or tailwind changes your speed more on gentle climbs than steep ones.
- Rough or gravel surfaces add rolling resistance and slow you down.
- Altitude lowers your sustainable power on high climbs.
- Fatigue: a climb late in a long ride takes longer than the same climb ridden fresh.
- Heat can lower the power you can hold on long, exposed climbs.
Ask LeCoach what power to hold on the climbs of your next event, and it answers from your own power profile and FTP.
Sources
- Fiets magazine. Fiets climb difficulty index (Fiets index): H² ÷ (D × 10) + (T − 1,000) ÷ 1,000.
- Martin JC, Milliken DL, Cobb JE, McFadden KL, Coggan AR. Validation of a mathematical model for road cycling power. Journal of Applied Biomechanics, 1998;14(3):276-291.
How hard are the famous climbs?
How hard is Alpe d'Huez?
Alpe d'Huez is 13.8 km at an average of 7.8 %, gaining 1,071 m to a summit at 1,850 m. Its Fiets index of about 9.1 puts it in the legendary band, driven mainly by the steady steep gradient through the 21 hairpins rather than extreme altitude.
How hard is Mont Ventoux?
From Bedoin, Mont Ventoux is 21.5 km long with 1,610 m of gain to a summit at 1,910 m, averaging about 7.5 %. The length is what makes it brutal: over 20 km at altitude with little shelter from wind, it punishes anyone who goes out too hard in the forest section before the exposed moonscape near the top.
How hard is the Stelvio?
The Stelvio from Prato is the longest and highest of this group: 24.3 km, 1,808 m of gain and a summit at 2,758 m, at an average of about 7.4 %. The altitude alone lowers your sustainable power over the final hour, on top of nearly 50 hairpins.
How hard is the Col du Tourmalet?
From Luz-Saint-Sauveur, the Tourmalet is 19 km at an average of about 7.4 %, climbing 1,404 m to 2,115 m. It is a classic Tour de France summit finish, steady rather than savage, but long enough that pacing the first half conservatively matters.
How hard is the Col du Galibier?
From Valloire, the Galibier is 18.1 km with 1,245 m of gain to 2,642 m, averaging about 6.9 %. It often follows other climbs in a stage, and the thin air near the summit makes the final kilometres feel harder than the gradient alone suggests.
How hard is the Mortirolo?
From Mazzo, the Mortirolo is short at 12.4 km but relentless, with 1,300 m of gain to a summit at 1,852 m, an average of about 10.5 % and ramps well into the mid-teens. It is widely rated among the hardest climbs in professional cycling for its sustained steepness rather than its length.
Frequently asked questions
How do I calculate the gradient of a climb?
Divide the elevation gain by the distance and multiply by 100, with both in the same unit. A climb that gains 700 m over 10 km (10,000 m) has an average gradient of 700 ÷ 10,000 × 100 = 7 %. Remember that this is an average: sections can be much steeper.
What is VAM in cycling?
VAM is your average vertical climbing speed in metres per hour. Divide the height you climbed by the time it took, in hours. Climbing 700 m in 44:15 is a VAM of 949 m per hour. On steep climbs it tracks watts per kilo closely, which makes it a useful fitness marker.
How long will a climb take me?
It depends mainly on the climb's height, your power and your total weight. At 250 W with 84 kg of rider, bike and kit, a 10 km climb at 7 % takes about 44 minutes. At 200 W it takes about 54 minutes, and at 300 W about 38 minutes. Enter your own numbers above.
What is the Fiets index?
It is a difficulty score for climbs from the Dutch magazine Fiets: gain² ÷ (distance × 10), plus (summit − 1,000) ÷ 1,000 for summits above 1,000 m. Under 2 is easy, 4 to 6 is hard and over 8 is legendary. Alpe d'Huez scores about 9.1.
Is it better to gain power or lose weight for climbing?
On a steep climb, both help by about the same amount per percent. On the example climb, 5 % more power saves 1:55, while losing 2 kg, about 2.4 % of the total, saves 0:55. Power is usually easier to gain without hurting your health or performance, so do not chase weight loss at the cost of training.
How hard is Alpe d'Huez?
On the Fiets index it scores about 9.1, which puts it in the legendary band above 8 and far above the 5.1 of the example climb. To estimate your own time, enter its length, gain and summit altitude in the calculator with your power and weight.
What power should you hold on that climb?
Get a plan that builds your climbing, with every workout set from your own FTP.
Try LeCoach for freeIn this topic
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