How we rate event difficulty
Every event page shows a difficulty score and a pacing & fuel plan. Here is exactly how they are computed — no black box.
The Ridium Difficulty Index (RDI)
Most rating systems approximate difficulty with a geometric formula (distance plus climbing, minus a descent discount). Ridium instead computes the actual physical work with its cycling-physics engine over the route's real GPX, so the score is intrinsic to the route, not to whoever is asking. Because gravity work grows with every metre climbed, the index weights climbing heavily and naturally.
Computed for a fixed reference rider, riding self-paced. Bike weight is slightly higher on gravel and MTB.
Methodology version: rdi-v2
Pacing & fuelling
From the same reference-rider estimate we derive a target effort for each notable climb and an hourly fuelling plan. Effort is given as a percentage of your own FTP, so you scale it to your fitness.
Climb effort by gradient| Band | Avg gradient | Target |
|---|---|---|
| Tempo | < 4% | 80–90% |
| Threshold | 4–7% | 88–98% |
| VO2 | ≥ 7% | 95–110% |
The per-climb target is then adjusted for the climb's length, its position in the route, and its altitude: long, late, or high-altitude climbs are paced more conservatively, while short early pitches allow a brief surge above threshold.
Carbohydrate by duration| Time on bike | Carbohydrate |
|---|---|
| ≤ 1.5 h | 30–60 g/h |
| 1.5–4 h | 60–90 g/h |
| > 4 h | 80–100 g/h |
| Conditions | Fluid | Sodium |
|---|---|---|
| Cold ×0.8 | 400–600 ml/h | 400–550 mg/h |
| Cool ×1.0 | 500–750 ml/h | 500–700 mg/h |
| Mild ×1.0 | 500–750 ml/h | 500–700 mg/h |
| Warm ×1.3 | 650–1000 ml/h | 650–900 mg/h |
| Hot ×1.6 | 800–1200 ml/h | 800–1100 mg/h |
Fluid and sodium scale automatically with the event's typical conditions; carbohydrates track duration only.
Weather normals
Each event shows typical conditions for its month. We read the climatology from Open-Meteo's open data (not the hosted API) for the cell over the route, then downscale the temperature to the route's real elevation with a constant lapse rate — so a valley start reads warmer than a high pass.
These are recent climatological normals over the available years, not a forecast — disclosed per event.
Methodology version: weather-normals-v1
Open-Meteo · ERA5/Copernicus (CC BY 4.0)
These figures are route-intrinsic estimates for a reference rider. Your personal finish time and fuel scale with your own fitness — run the simulator for a personalised plan.
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