What is Grade Adjusted Pace?
Running uphill is harder than running on flat ground and downhill isn't always easier either. Grade Adjusted Pace (GAP) is a way of normalizing your pace so you can compare efforts across hilly and flat terrain on equal terms. Instead of seeing a slow pace on a steep climb and a fast pace on a descent, GAP translates every moment of your run into what that effort would feel like on flat ground.
The Science Behind It
GAP is calculated using a formula developed by Alberto Minetti and colleagues, based on research into the energy cost of running at different gradients. The formula estimates how much energy (in joules per kilogram per meter) your body uses at a given slope:
Energy Cost = 155.4i⁵ − 30.4i⁴ − 43.3i³ + 46.3i² + 19.5i + 3.6
Where i is the gradient expressed as a decimal (e.g. a 10% grade = 0.10).
On flat ground (i = 0), the formula produces a baseline energy cost of 3.6 J/kg/m. Every other gradient is then compared to that baseline. A steep uphill has a much higher energy cost than flat ground, so your GAP will be slower than your actual pace, reflecting the extra effort you're putting in. A gentle downhill may have a slightly lower cost, nudging your GAP a little faster.
How the Calculation Works
For each moment of your activity, we pair your actual speed with the gradient at that point in time. The gradient comes from your GPS altitude data and is matched to your speed data.
The adjustment is then straightforward:
GAP Speed = Actual Speed × (Energy Cost / 3.6)
This scales your speed up or down depending on whether the terrain was harder or easier than flat. The result is expressed as a pace, just like your regular pace, so it's easy to interpret.
What This Means in Practice
Terrain | Effect on GAP |
|---|---|
Flat ground | GAP ≈ actual pace |
Steep uphill | GAP is slower than actual pace (you're working harder than your pace suggests) |
Gentle downhill | GAP may be slightly faster than actual pace |
Very steep downhill | GAP may be slower again (extreme descents also increase energy cost) |
That last point surprises many runners; Minetti's research shows that extremely steep descents actually require more muscular effort to brake and control, so GAP accounts for this too.
A Note on Accuracy
GAP is an estimate based on a well-validated physiological model, but individual runners vary. Factors like running economy, fatigue, terrain surface, and footwear aren't captured in the gradient alone. Think of GAP as a strong approximation of effort a useful training tool, not an exact measurement. If you have suggestions on how we can improve GAP, by using a different formula, or other means, feel free to let us know at dev@tracka.sport.
