AI ESTIMATOR
Trail time estimator
How long will your trail take? Enter your race and your ITRA, UTMB or B-Trail index: our estimator computes your finish time by comparing your profile to real runners on the same event. Distance, elevation gain (D+), pace, aid stations and cut-off times are all factored in for a realistic race-time estimate.
AI ESTIMATOR
Estimate your race time
AI searches for similar runners in the ITRA, UTMB and B-Trail databases to estimate your finish time.
Mid-pack, several races finished. Estimate anchored on the median corrected for DNF bias.
Default: 5 min per aid station. Slide to override.
THE METHOD
Estimate your trail time, for real
Calculating your trail race time is more than a slope rule. Distance, elevation gain (D+), terrain technicality, altitude, heat and fatigue all weigh on your real pace. Instead of a plain formula (Naismith, Borner, effort-km), we compare your ITRA, UTMB or B-Trail index to real finishers of the same event.
You get three scored scenarios — optimistic, realistic, conservative — a race plan with aid-station-by-aid-station splits, and what you need to check cut-off times. It's the time estimator closest to real-world conditions, not a theoretical average.
IN 30 SECONDS
How it works
- 1
Pick your race
UTMB, Maxi-Race, SaintéLyon, or one of our 200+ referenced races.
- 2
Enter your level
ITRA score, UTMB Index or B-Trail. Or your latest reference time.
- 3
Get your estimate
Three possible times, aid-station breakdown, links to comparable runners.
3 SCENARIOS
Optimistic, realistic, conservative.
Three finish windows for the same race. Pick the one that matches your strategy.
Optimistic
Realistic
Conservative
SOURCES
Not an average — a triangulation.
ITRA
Points and performance index from your latest season.
UTMB Index
Official performance index from UTMB World Series.
Similar profiles
Runners with a comparable profile who already finished this race.
FAQ
Is it really free?
Yes. Magic-link sign-in so we can let you know when we ship updates.
How accurate?
On referenced races, the estimate usually lands within ±15% of real time — much better than a slope-based formula.
What if my race isn't listed?
Add it in two steps: its name and a GPX track. The file provides the distance and elevation gain (D+), we run the estimate right away, and the race joins the goodborning database. No email required.
How long does a 20, 50 or 80 km trail take?
It depends mostly on elevation gain and your level. As a rough guide: a 20 km trail often takes 2 h to 3 h 30, a 50 km 6 h to 10 h, an 80 km 10 h to 16 h. The estimator refines this with your race's real D+ and your index.
What are effort-km and flat-equivalent distance?
Effort-km (or effort distance) converts elevation gain into an equivalent flat distance. The common ITRA formula: effort-km = distance (km) + D+ (m) / 100. Handy to compare two races' difficulty, but the estimator goes further by using real finisher times.
How do cut-off times work?
A cut-off time is a deadline at a checkpoint: miss it and you're out of the race. The aid-station-by-aid-station splits help you check that your target pace keeps you ahead of every cut-off.
Why is this better than a slope formula?
A slope formula (Naismith, Borner, 100 m D+ = 1 km flat) ignores technicality, altitude, heat, night and your real level. By comparing your index to comparable finishers, the estimate usually lands within ±15% of real time on referenced races.
NOT A REFERENCED RACE?
You just have a GPX track
Personal recon, private event, unlisted course: we estimate your time directly from the GPX file and your level.
Estimate from a GPX