Race time and pacing

Your likely finish time from your current fitness, and the pace to hold on each leg to get it.

Race distance

How do you want to race it?

Swim

What do you know?

Pace per 100 m you can hold for 1500 m (m:ss)Your threshold pace, also called CSS, in a pool.

Wetsuit

Bike

FTP (watts)Functional threshold power: the most you can hold for about an hour. From a power meter or smart trainer test.

Your weight (kg)Shared with the tyre pressure and fuelling tools.

Riding position

Course

Rolling is about 6 m of climbing per km (240 m over 40 km), hilly about 12 m per km.

Run

A recent race or hard run

Your time (h:mm:ss or mm:ss)On fresh legs, from the last 3 months. Not a run off the bike.

Add your swim pace, your FTP, your weight and a recent run time to see your finish time.

How this is worked out

Swim. Your threshold pace, or critical swim speed (CSS), is about the pace you can hold for 1500 m. From test times it is (400 m time minus 200 m time) divided by 2, per 100 m (Wakayoshi and others, 1992). Over longer swims we add 1 to 2 seconds per 100 m (Swim Smooth). A wetsuit makes you about 4% faster (3.7% over 1500 m across 26 studies, Gay Párraga, 2022).

Bike. Race power is a share of your FTP that falls as the race gets longer: 88 to 98% for a sprint, 85 to 95% for an Olympic, 72 to 85% for a 70.3 and 60 to 75% for a full (TrainingPeaks). Speed comes from the standard physics of cycling (air drag, rolling resistance and drivetrain losses), which matched measured power within about 3 W in a 1998 validation study (Martin and others). Drag depends mostly on your position; we use typical values for age-group riders (Best Bike Split).

Run. Your recent run is scaled to the race distance with Riegel's formula (1981). It works well up to the half marathon but is often too optimistic for the marathon (Vickers and Vertosick, 2016). Running off the bike is slower again: studies of short runs find 2 to 6%, and no study has measured it for a full distance marathon (Tsutsumi and others, 2026).

Our own estimates, which we will tune as results come in: open water about 3% slower than the pool; how much climbing "rolling" and "hilly" mean, and that half the climbing effort comes back on the descents; a 9 kg bike with bottles; the run fade off the bike (3% sprint, 4% Olympic, 8% 70.3, 15% full); transition times; and the 5% range either side of the finish time. The pacing tips are common coaching advice. Wind, heat, rough roads and a crowded swim can all add time.