Custom course pace calculator
Upload your own race course, choose the race distance and add the start temperature you expect. The calculator turns your flat-course ability into an equal-effort pace and split plan for the hills and heat on that course.
- 1Upload a courseGPX track points or a FIT course with elevation.
- 2Set the dayPick the race distance, start temperature and dew point.
- 3Run the planGet an equal-effort time, average pace and splits.
Upload your course
How the estimate works
- GPX track, route or waypoint elements and FIT record messages are read in the browser. The file is never uploaded to a server.
- The route is measured from its coordinates, smoothed over about 320 m and resampled to 25–100 m segments so GPS elevation noise does not read as hills.
- If you choose a standard race distance, the track is stretched to that distance. Otherwise the file’s measured distance is used.
- Each segment runs at your flat-course pace times a grade factor: about +3.3% per 1% uphill and −1.8% per 1% downhill, with the downhill gain fading on steep descents.
- Heat is scored with shade WBGT from your start temperature and dew point, held constant through the race. Wind, sun, rain and how your pacing changes late in the race are not modelled.
- These are planning estimates, not guarantees. Use the splits as a starting point and adjust for crowding, turns and how you feel on the day.
Frequently asked questions
Which file types can I upload?
GPX files with track, route or waypoint coordinates, and FIT course or activity files with record messages. The file is read locally in your browser; it is not sent to a server. A course with elevation points produces the most accurate terrain adjustment.
How is the equal-effort pace calculated?
The uploaded track is smoothed and cut into short segments. Each segment is run at your flat-course pace times a grade factor, with climbs costing about 3.3% per 1% uphill and descents giving back about 1.8% per 1% downhill. A heat factor from shade WBGT is applied at the time you reach each segment, then all the pieces are added to get the course time.
Why is the full temperature held constant?
A single uploaded start temperature has no hourly forecast behind it, so the model applies that reading for the whole race. If you expect a large warm-up, enter a value closer to the middle of your race or switch the temperature off to see the terrain-only estimate.
What if my GPX has no elevation data?
The calculator still works, but treats the course as flat. Add elevation points to the GPX or use a FIT file with altitude records to include climbs and descents.
Can I use a half marathon, 10K or 5K course?
Yes. Choose the race distance after uploading. If the file is close to a standard distance it is selected automatically; otherwise you can keep the file's measured distance. The track is stretched to the chosen distance so pace and split labels match the race.