Last updated: 2026-06-21

Comparing Hills and Flats Fairly

Pace alone lies on hilly terrain. A 5:30-per-kilometre climb can be a harder effort than a 4:30-per-kilometre stretch on the flat, yet the stopwatch makes the climb look slow. Grade-adjusted pace fixes this by translating your hill pace into the flat-ground pace that would have cost the same energy, so every part of a run can be judged on equal terms.

This calculator uses the Minetti model, a well-known measurement of how much energy running costs at different gradients, to do that conversion from a single pace and a slope.

How It Works

Minetti and colleagues measured the metabolic cost of running — energy per kilogram of body mass per metre travelled — across a wide range of gradients and fitted it to a curve. With the grade written as a fraction $i$ (so a slope of $i = 10\%$ enters as a tenth), the cost in joules per kilogram per metre is:

On the flat the gradient is zero and the cost is $C(0) = 3.6\ \text{J/kg/m}$. Holding effort fixed, the flat-equivalent pace scales your actual pace by the ratio of flat cost to slope cost:

When the slope costs more than flat ground, that ratio is below 1 and the adjusted pace comes out faster than what you ran — the calculator is crediting you for the extra work.

Worked Example

Take a steady climb at a 10% grade.

At a grade of $i = 10\%$ the Minetti cost is about $5.97\ \text{J/kg/m}$, against $3.6\ \text{J/kg/m}$ on the flat. Running 5:00 per kilometre uphill therefore adjusts to roughly $5.0 \times 3.6 / 5.97 \approx 3.01$ minutes per kilometre — a flat pace of about 3:01 per kilometre. The slow-looking climb was a genuinely hard effort. At a grade of $i = 10\%$ the Minetti cost is about $5.97\ \text{J/kg/m}$, against $3.6\ \text{J/kg/m}$ on the flat. Running 8:03 per mile uphill adjusts to roughly $8.05 \times 3.6 / 5.97 \approx 4.86$ minutes per mile — a flat pace of about 4:51 per mile. The hill made an honest effort look much slower than it was.

Reading the Result

• Uphill always adjusts to a faster flat pace, and the steeper the climb the larger the gap.
• Gentle downhills adjust to a slightly slower flat pace, because losing a little height saves energy.
• Steep downhills stop being free: braking forces drive the cost back up, so the adjustment shrinks again.

When to Trust It

The Minetti curve is built from treadmill running at a constant gradient, so it describes the average energy cost of a clean, steady slope well. Trail footing, sharp switchbacks, soft ground, and the fatigue that builds over a long climb are beyond what a single equation can capture. Use grade-adjusted pace to compare efforts across varied terrain and to pace climbs sensibly, while remembering it is a model of the average runner, not a personal measurement.