What problem this solves
A flat-pace calculator tells you 6:30/km and that's it. Useless on a course with 800 m of climb, because a 6:30/km on rolling terrain is wildly different from 6:30/km on a road. Grade-Adjusted Pace (GAP) translates your climb-descent effort into a flat-ground equivalent — so you can compare two runs objectively.
This tool uses the Minetti et al. (2002) energy cost of walking/running on gradients, scaled by your body weight and surface factor. We surface three numbers because racers actually use all three: actual pace (race results), GAP (training comparability), and an effort score (qualitative pacing).
Who this is for
- Trail racers comparing training blocks across different courses.
- Coaches who want one number to track athlete progress on varied terrain.
- Backyard ultra / ultra-runners planning aid-station splits where grade dominates.
- Curious hikers who want to know how much harder a climb actually was.
How to interpret the output
Actual pace is what your GPS watch shows. GAP is what you'd run on flat ground for the same effort — typically faster than actual pace on climbs, slower on descents. For example, a 7:00/km trail pace with 600 m gain over 15 km may translate to a 5:40/km GAP, telling you your flat fitness is strong but your climbing form has room to grow.
Effort score is a 0–100 index we compute from GAP vs your flat baseline (assuming a 5:00/km flat-equivalent fitness, adjustable in your head). Anything over 70 is a serious effort; under 40 is easy cruising.
Limitations
- The Minetti model was developed for treadmill walking/running on known grade. Real trails add uneven terrain, footing instability, and weather — your real cost will be higher.
- Surface factor is a rough multiplier; true surface energy can vary ±20%.
- Doesn't account for wind, altitude, dehydration, or fatigue over the course.
- Downhill GAP is less validated than uphill — treat the descending side as a directional estimate.
FAQ
Why use GAP instead of pace?
GAP normalizes out elevation so two runs on different terrain can be compared fairly. Strava and UTMB use a related metric (Power / GAP) for the same reason.
What if my distance has rolling terrain?
Enter total gain + total loss. The model averages the cost of all climb segments and descent segments across the full distance.
Is this the same as Strava's "Grade-Adjusted Pace"?
Same concept, slightly different formula. Strava's GAP uses a proprietary curve. We use Minetti because it's the published, peer-reviewed version. For most uses the two will agree within 5%.