Zwift Climb Time Calculator
Pick any sustained climb in the game, put in your weight and the power you can hold, and get a time. Unlike the Alpe du Zwift calculator, which is fitted to real finishing times on one specific climb, this one runs the physics from first principles, so it works anywhere. The full equation and every constant it uses are written out below.
19 km, 1481 m of climbing, 7.8% average as published. This model uses 7.8%, which is the gain divided by the distance.
Height only affects the aerodynamic term, which is close to irrelevant on a steep climb and starts to matter on shallow ones. Zwift does not publish the weight of its in-game frames, so 9 kg is a reasonable stand-in for bike, wheels, shoes and kit rather than a known value.
Estimated time
1:24:04
Realistically somewhere between 1:19:51 and 1:28:16
- Power-to-weight
- 3.33 W/kg
- Average speed
- 13.6 km/h
- VAM
- 1057 m/h
- Spent on drag
- 3.4%
Where your power goes
Gravity 92%, rolling 5%, drag 3%. This split is the whole reason W/kg matters more than watts on a climb.
Ventoux KOM (Mont Ventoux) at every power-to-weight ratio
Same climb, same 75 kg rider, different sustainable power. Use it to see what a training block would actually buy you.
| W/kg | Watts at 75 kg | Estimated time |
|---|---|---|
| 2.0 | 150 W | 2:17:07 |
| 2.5 | 188 W | 1:50:28 |
| 3.0 | 225 W | 1:32:50 |
| 3.5 | 263 W | 1:20:19 |
| 4.0 | 300 W | 1:11:01 |
| 4.5 | 338 W | 1:03:50 |
| 5.0 | 375 W | 58:08 |
| 5.5 | 413 W | 53:30 |
The equation this uses
A rider climbing at a steady speed is fighting three forces. Gravity pulls the combined mass of rider and bike back down the slope. Rolling resistance opposes the tyres turning. Air drag opposes forward motion. At a constant speed the power you produce exactly balances the sum of the three:
This is the steady-state form of the road-cycling power model validated by Martin and colleagues in 1998, with the acceleration and kinetic-energy terms dropped because a sustained climb has no meaningful speed change. The equation is a cubic in v, so the calculator solves it numerically rather than in closed form, then divides the climb distance by the resulting speed.
The constants
| Symbol | Value | Where it comes from |
|---|---|---|
| g | 9.8067 m/s² | Standard gravity. Not in dispute. |
| ρ | 1.22601 kg/m³ | Air density. Zwift appears to hold this fixed rather than thinning the air as you climb. Community-derived, not published by Zwift. |
| Crr | 0.004 | Rolling resistance for road wheels on tarmac, from community timed testing. Gravel and dirt are considerably higher, which is why this calculator only offers paved climbs. |
| CdA | 0.3016 m² | Drag area for your height and weight, from body-surface-area scaling multiplied by a drag coefficient of 0.889. Estimated, not measured. |
| m | 84 kg | Your weight plus bike and kit. |
| k | 0.9524 | A single calibration multiplier on the final time, fitted so the model reproduces the best public Alpe du Zwift reference times. |
Why there is a calibration constant at all
Zwift has never published its physics engine. It has never published the drag area it assigns your avatar, the rolling resistance of each surface, or the weight of a single in-game frame. Everything the community knows has been recovered by riding controlled tests and working backwards.
That means a first-principles model built from public numbers will be systematically off by a few percent, and it is more honest to say so and correct for it than to quietly tune a physical constant until the answer looks right. So the raw physics runs, and then one clearly-labelled multiplier of 0.9524 scales the result.
That constant was fitted by comparing the model against the best publicly available Alpe du Zwift time estimates across 3.0 to 6.5 W/kg. After calibration the model sits within about 1% of that reference on average, and within 4% at its worst point. Below 3 W/kg it drifts further, because the reference data itself thins out down there.
Which calculator should you use?
For Alpe du Zwift and Ven-Top, use the dedicated calculators. They are fitted directly to observed finishing times on those climbs, so they capture whatever the physics model misses. Use this page for everything else, and for understanding why the numbers land where they do.
What the model cannot see
- Your pacing. It assumes you hold the power you entered for the entire climb. Almost nobody does on their first attempt at a long ascent, and the cost of going out too hard is far larger than any modelling error here.
- Descents inside a segment. Several timed segments include short downhill sections. Their published elevation figure is total gain, so dividing it by the distance overstates the real slope and the model comes out slow. The climbs where this matters most are the shallow, rolling ones.
- Surface changes. A few climbs switch to dirt, ice or snow partway up, all of which roll slower than tarmac. This calculator assumes tarmac throughout.
- The draft. On anything steep the draft is close to irrelevant, which is why it is ignored here. On the shallow climbs in the list it is not, and riding in a group will beat this estimate.
- Your equipment choice in game. Frames and wheels carry different weight and drag values that Zwift does not publish.
- Heat, hydration and how your day is going. These are worth more minutes than every parameter above put together.
If your real time disagrees with this by more than a few percent, that is genuinely useful to know - send the numbers over and the model gets better. The editorial policy explains how corrections are handled.