Running calculator
Grade adjusted pace calculator
What your hill running is worth on the flat. Enter the pace you held and the gradient you held it on, and get the equivalent level pace — per kilometre and per mile. Free, instant, no sign-up.
A 5% climb costs 1.3× as much per metre as level ground, so 5:00/km up it is worth 3:51/km on the flat — the hill is buying you 1:10 per kilometre.
Hilly routes wreck flat-pace targets — the coach sets efforts your terrain can actually deliver.
What is grade adjusted pace?
GAP answers one question: if I had run this effort on flat ground, how fast would I have been going? It exists because pace stops measuring effort the moment the ground tilts. Two runs at 5:00/km — one up a 5% grade, one on a track — are not the same run, and only one of them is a 5:00/km effort.
How this calculator works
We use the energy cost of running measured by Minetti and colleagues (Journal of Applied Physiology, 2002), who ran athletes on a treadmill tilted from -45% to +45% and fitted a fifth-order polynomial to the oxygen cost: Cr = 155.4i⁵ − 30.4i⁴ − 43.3i³ + 46.3i² + 19.5i + 3.6 joules per kilogram per metre, with i the gradient as a fraction. Level running costs 3.6 J/kg/m. Equal effort means equal energy per second, so the flat-equivalent pace is your pace scaled by 3.6 divided by the cost of your gradient — a factor of 1.30 at 5%, and 1.66 at 10%.
Why downhill is not free
The shape of that curve is the reason to use a measured model instead of a rule of thumb. Cost falls as the ground drops away, but only to about -20%, where a metre costs 1.8 J/kg — exactly half the flat. Past that it climbs again: on a steeper descent you are braking with every stride rather than falling forward, and by -45% the model has descending costing more than running on the level. Anyone who has come down an alpine trail already knows this in their quadriceps.
Using GAP in training
Use it to compare efforts, not to set them. A hilly long run at 5:30/km that grades to 5:05/km tells you the session was worth more than the watch said, which matters when you are tracking a block of training week over week. Be careful at the steep end: the model prices the energy, not the biomechanics, and it will cheerfully tell you that a 20% climb at 8:00/km is worth 3:12/km on the flat — a pace your legs could not produce on any surface. Past about 10%, treat the number as a direction rather than a target.