Hills lie. GAP tells the truth.
Type your actual pace on a hill and the grade. We calculate your flat-equivalent pace — the speed you’d need on flat ground to match the same effort.
At 5:30/km on 5% grade, your flat-equivalent pace was 4:36/km.
Grade-adjusted pace (GAP) is the flat-ground pace that would have demanded the same metabolic effort as your actual hill running pace. Trail runners use it to compare workouts across different terrain. Strava popularized the metric; the underlying physics goes back to research by Minetti et al. on the energetic cost of gradient running.
How the equivalent flat pace changes for a 5:00/km actual pace across common grades. Use as a sanity check.
| Grade | Actual pace | Flat equivalent |
|---|---|---|
| -10% | 5:00/km | 6:12/km |
| -5% | 5:00/km | 5:50/km |
| -3% | 5:00/km | 5:30/km |
| 0% | 5:00/km | 5:00/km |
| +3% | 5:00/km | 4:30/km |
| +5% | 5:00/km | 4:11/km |
| +8% | 5:00/km | 3:48/km |
| +10% | 5:00/km | 3:33/km |
GAP is a model. Real energy cost varies with surface (concrete vs trail), wind, altitude, fatigue and individual biomechanics. Treat it as a normalization tool, not a precise measurement. For race-day pacing on hilly courses, train on similar terrain.
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Convert pace, finish time and distance for any race from 5K to ultra. Includes split times and predicted race times.
Type a recent race result and we predict your finish time at every standard distance — 5K, 10K, half marathon, marathon and beyond.
Turn treadmill speed and incline into min/mile, min/km and outdoor-flat-equivalent pace.
Pick a target finish time and split strategy. Get first/second-half splits and every-5K targets to print on your wrist.
Anytime you want to compare workouts across different terrain. A 5:00/km on flat is not the same effort as 5:00/km uphill — GAP tells you the equivalent flat pace so you can judge fitness consistently.
We use a linear approximation of Strava’s GAP curve: GAP ≈ pace × (1 − 0.033 × grade%) for grades up to ±5%, then taper for steeper terrain. The original Minetti polynomial is more accurate but harder to communicate.
Up to about 6% downhill, yes — gravity helps. Beyond that, eccentric muscle damage from braking starts to make it harder. Steep descents in races are often the leg-killer that ends marathons and ultras.
Strava recalculates grade each second using GPS + barometer, so it averages many small grades. Our calculator uses a single grade you specify. For climbs with rolling terrain, Strava will be smoother.