Trail Running Pace Calculator & Grade Adjusted Pace (GAP)

Free trail running pace calculator and grade adjusted pace calculator. Convert your flat road pace into a realistic trail pace for any elevation profile, get an estimated finish time, and read your grade adjusted pace (GAP) for every gradient from -20% to +30%. Complete result, no account required.

For benchmark paces by level and terrain, see the trail running pace guide: https://trailia.run/guides/training/trail-running-pace-guide-calculator. For a finish time based on a recent race result, use the race time predictor: https://trailia.run/tools/race-predictor.

How It Works

Enter a flat pace you can hold for the duration of the effort
Add the course distance, elevation gain and loss
Choose how technical the surface is
Read your trail pace, finish time, climb and descent paces, and the full GAP table

The Model

The course is split into a climbing portion and a descending portion, sized by how much of the total vertical movement each accounts for. Each portion's average gradient runs through the Strava-aligned grade-adjusted pace speed factors — the same model Trailia uses throughout the app, rather than the Minetti energy-cost curve most free calculators use. The two paces are recombined into a finish time, then a terrain multiplier is applied:

Terrain	Multiplier
Runnable (smooth path, fire road)	1.00x
Moderate (singletrack, some roots)	1.08x
Technical (rock, scree, steps)	1.18x
Very technical (alpine, hands needed)	1.30x

Grade-Adjusted Pace

Grade adjusted pace converts your actual pace on a slope into the flat-ground pace that would have taken the same effort. Running 7:30/km up a 10% grade is roughly a 5:10/km flat effort.

Hike Crossover

For most runners, hiking becomes as fast as running somewhere between 15% and 20% gradient, at a much lower metabolic cost. The crossover comes down on technical ground and comes down further with fatigue, which is why power hiking is a trainable skill that decides long mountain races.

Km-Effort

ITRA's course difficulty measure: distance in kilometres plus elevation gain in metres divided by 100. A 42 km race with 2000 m of gain is 62 km-effort.

Limitations

The course is modelled as one average climb and one average descent. A race with a single brutal 1500 m ascent runs slower than the estimate; a rolling course of the same gain runs faster. Upload the GPX to the pacing planner when the distribution matters.
GAP describes effort, not endurance. It does not know you will be six hours in and cooked — that is what the race predictor is for.

FAQ

How much slower is trail running than road running? It depends on vertical gain and surface, not on it being a trail. A rolling forest path might cost 15-20% per km; a technical mountain course can double your road pace.

Which GAP model does this use? The Strava-aligned speed-factor curve, so the numbers line up with what you see in your Strava activity feed.