Method

How it works

No magic: open data, a couple of published formulas and a good deal of care. This is what sits behind every race sheet.

Course tracks

No course is drawn by eye. Each one comes from a GPS recording of the latest edition (Seville 2026, Madrid 2026, Valencia 2025, San Sebastián 2023, unchanged since 2022) or, for Barcelona, from the official 2026 map rebuilt over OpenStreetMap. GPS recordings measure 1-2% more than the certified 42.195 m, so kilometre marks are spread proportionally over the official distance.

Elevation

Altitude comes from the European EU-DEM 25 m terrain model, sampled every 25 m along the track and smoothed over 300 m windows. Cumulative gain only counts climbs and descents of more than 3 m in a row, which is what a barometric watch does. In Madrid, where we have a barometric recording, the mean difference to the model is 2 m.

Pace band

An even-pace band makes you suffer on the climbs and waste time on the descents. Ours spreads your goal time over the kilometres using the energy cost of running on gradients from Minetti et al. (2002): each kilometre gets a weight from its climb and descent, so effort stays even and the total is yours. The negative split and conservative start strategies apply a linear 2% drift between the halves. Clock time adds the elapsed split to your wave start time.

Gel plan

Taking a gel with no water at hand is the recipe for an upset stomach. From your carbohydrate rate and the carbs per gel the interval between intakes is computed. Each intake is placed at the nearest aid station with water, between 600 m before and 1.5 km after the theoretical point, using your pace band. Current guidelines recommend 60-90 g per hour for efforts over two and a half hours, provided you have trained it.

Weather

Nobody knows what the weather will do on your race day, but we do know what it usually does. ERA5 reanalysis statistics (Open-Meteo) from 1996 to 2025 over a seven-day window around the race date, at the start hour and three hours later. This is climatology, not a forecast: it says what is usual, not what will happen.