Enter your weight, your bike's weight, the average gradient, the surface, how much of the time you sit in the draft and your average speed. The calculator estimates your average power in watts, your W/kg, your VAM, the elevation gained and the calories burned, with a breakdown of where every watt goes.
Time you would gain or lose on this same climb by changing one single thing.
| Change | watts | Time | Diff. |
|---|
With the same watts and the same weight you entered above, this is roughly how long you would take on some of the most famous climbs in cycling. Click a climb to load its data into the calculator.
| Climb | Dist. | Grad. | Elevation | Your time | Speed |
|---|
Approximate distance and average gradient from the classic starting point of each ascent. Times assume a constant gradient and ignore flatter recovery sections and the steepest ramps.
Climbing is, physically, a balance problem: the power you put through the pedals is split between three resistances. On the flat aerodynamics dominates; beyond 5-6 % gradient, gravity takes almost everything.
Gravity (m·g·sin θ·v). Depends on total weight —you plus the bike, bottles and whatever is in your pockets— and on the gradient. It is the dominant term on any serious climb, and the reason one kilogram matters so much uphill and almost nothing on the flat.
Rolling resistance (Crr·m·g·cos θ·v). The deformation of the tyres against the road. The Crr coefficient depends on the tyre, the pressure and above all the surface: rough tarmac can double the resistance of smooth tarmac, and gravel triples it.
Aerodynamics (½·ρ·CdA·v_air²·v). Grows with the cube of speed, so at 14 km/h on a climb it is barely 5-10 % of the total, while at 40 km/h on the flat it is more than 80 %. Air density ρ falls with altitude, which makes climbing at 2,500 m aerodynamically cheaper.
Efficiency (η). The chain and bearings eat 2 to 4 % of what you put into the pedals. The default here is 97.5 %, typical of a clean, well lubricated drivetrain.
| Surface | Crr | Notes |
|---|---|---|
| Smooth tarmac / new road | 0.0035 | Race tyres at proper pressure |
| Average tarmac | 0.0050 | Default value for road |
| Poor tarmac | 0.0070 | Cracks, patches, aged surface |
| Cobbles / pavé | 0.0100 | Highly dependent on pressure and width |
| Hard-packed gravel | 0.0090 | Forest road in good condition |
| Loose gravel | 0.0140 | Loose stones, sand |
| Dirt / trail | 0.0180 | MTB, soft ground |
Less than people think. The draft only acts on the aerodynamic term, and on a climb that term is small. Sitting in the wheels the whole way at 14 km/h on an 8 % gradient saves a handful of watts; on the flat at 40 km/h that same draft can be worth 80 W or more. That is why breakaways survive in the mountains and not on the flat.
VAM (velocità ascensionale media) is the metres of elevation you gain per hour. It is the classic metric for comparing climbers without a power meter: a trained recreational cyclist sits around 800-1,000 m/h, a fast amateur 1,100-1,300 m/h, and a World Tour professional exceeds 1,600 m/h on a 40-minute climb. As a rough rule, W/kg ≈ VAM / (200 + 10 × gradient %).
| Level | W/kg (20-40 min) | Approx. VAM at 8 % |
|---|---|---|
| Occasional recreational rider | 2.0 – 2.8 | 560 – 780 m/h |
| Trained amateur | 2.8 – 3.6 | 780 – 1,010 m/h |
| Competitive amateur | 3.6 – 4.5 | 1,010 – 1,260 m/h |
| Elite / under-23 | 4.5 – 5.5 | 1,260 – 1,540 m/h |
| World Tour professional | 5.5 – 6.5 | 1,540 – 1,820 m/h |
The estimate on a climb is surprisingly good: once the gradient passes 5 %, more than 85 % of the power is explained by weight, gravity and speed alone, all of which you know precisely. The typical error is around 3-5 %. On the flat, by contrast, everything hinges on CdA and wind, and the error can blow up.
In "rider weight" put your body weight, and in "bike weight" include the bike, full bottles, helmet, shoes, jersey and whatever is in your pockets.
Important: W/kg is calculated by dividing power by your body weight only, excluding the bike. That is the universal convention —the one Strava, TrainingPeaks and professional performance estimates use— and it is the figure to compare against the level tables. The bike's weight does enter the watts calculation, because gravity pulls on the whole system, but never into the divisor. That is why a second figure is also shown, "W/kg (rider + bike)", which governs the physics of the climb but is useless for comparing yourself with anyone.
At the same speed on an 8 % gradient, each kilogram costs roughly 3 W at 14 km/h. Turned around, which is what matters: losing 2 kg on a 10 km climb at 8 % with the same power saves you about a minute. Use the "What if…?" table to see it with your own numbers.
Higher up the air is less dense, so aerodynamic drag falls. At 2,000 m the density is 21 % lower than at sea level. On a slow climb that is worth only a few watts; on the flat at high speed it is a meaningful difference. Note that the calculator models the physics of the air, not the physiological loss from reduced oxygen, which in an unacclimatised rider is far larger.
Yes. Pick the matching surface in the dropdown: rolling resistance is what changes most between road, gravel and dirt, and it can triple that term. Remember to include the extra weight of the bike and of a hydration pack.
The usual reasons are that the real average gradient is not constant (the steep sections weigh more than the average suggests), that mountain wind changes section by section, or that the default CdA does not match your size and position. Set a manual CdA in the advanced settings if you have a measured value.
If this one was useful, these three will be too.
CalculatorWork out your W/kg by duration, your level, your rider type, your critical power, your W′ and your training zones from your best 5 s, 1, 5, 20 and 60 minute efforts.
Open →
CalculatorEstimate frontal area from a photo and compare CdA, posture, aero helmet, deep wheels and sock assumptions. Approximate 3D model with local photo processing.
Open →
CalculatorAdjust your target pace for temperature, humidity and altitude, and find out why on a bike thin air makes you faster on the flat and slower on a climb.
Open →This calculator is an informational estimate and does not replace a coach or a laboratory test. Nothing you type ever leaves your browser.