Cycling Climb Time and VAM Calculator
How long a climb takes at a given power, with VAM, average gradient and where the watts actually go — validated against famous climbs.
Where the power goes
What this does and does not know
- It assumes a steady effort at a constant gradient. Real climbs have flat sections and ramps, and riding those at one power is not the same as averaging them.
- VAM depends on the road as well as the rider. The same person produces a higher figure on a steeper climb, because less power leaks into air resistance. Comparing VAM across different climbs flatters whoever rode the steeper one.
- Weight matters, and less than people spend on it. A kilogram off the bike is worth a handful of seconds on a long climb — real, and rarely worth what it costs against the same kilogram off the rider or a winter of training.
- Wind is not modelled, because on a climb it is unpredictable and often sheltered. On an exposed summit it can cost more than the gradient does.
How to use
- Enter the length and height gain, or pick one of the famous climbs.
- Enter the power you can genuinely hold for that long.
- Add rider and bike weight — both are lifted.
- Read the time, the VAM, and where the power is going.
Frequently asked questions
What is VAM?
Velocita ascensionale media — vertical metres climbed per hour. It was popularised by Michele Ferrari as a way of comparing climbing performances, and it is useful because it strips out how long a climb is: 1,000 metres an hour is the same effort whether the climb lasts twenty minutes or two hours.
Can I compare my VAM to a professional figure?
Only loosely, because VAM depends on the road as well as the rider. The same person produces a higher figure on a steeper climb, since less power leaks into air resistance at the lower speed — so comparing across different climbs flatters whoever rode the steeper one. Professional pace on a major climb is roughly 1,600 to 1,800.
How accurate is this?
Good, within its assumptions. It was checked against climbs with well-known times: a 62 kg rider at 400 watts comes out at 37 minutes for Alpe d'Huez, against a contested record of about 37 and a half. What it cannot know is that real climbs have flat sections and ramps, and riding those at one steady power is not the same as averaging them.
How much is a lighter bike really worth?
Less than the marketing implies and more than nothing. A kilogram off the bike saves a handful of seconds on a long climb — genuinely real, and rarely worth what it costs against the same kilogram off the rider, or against a winter of training. The tool lets you test it rather than argue about it.
Why does air resistance barely matter here?
Because it scales with the cube of speed, and climbing speeds are low. On a 10 per cent gradient the power going into lifting you outweighs the power going into air by well over ten to one, which is why an aero position is worth almost nothing on a steep climb and why the split is shown rather than assumed.
Does altitude make a difference?
Two opposing ones. Thinner air means less resistance, which is a small gain, and less oxygen means less power, which is a larger loss above roughly 1,500 metres. This models the air and not the physiology, so at altitude enter the power you can actually produce up there rather than your sea-level figure.
Why is the gradient slightly different from the one on the sign?
Signs and guidebooks often divide height gain by road distance, where the gradient is properly height over the horizontal run. The difference is under half a per cent on ordinary climbs and grows as the road steepens. This uses the horizontal run, which is why a very steep climb reads a shade higher here.
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