Effort-kilometre calculator
Convert distance and elevation into flat kilometres, with the terrain coefficient and a time estimate. To compare a trail with a road race.
Updated 16 September 2026
A 30 km trail with 1,500 m of climb has nothing to do with a 30 km road race. The effort kilometre brings both to the same scale, so you know what you are signing up for and how long you will be out.
It is also the tool that prevents the classic training mistake: building long runs around the race distance rather than its real cost, and arriving on race day with legs that have never worked three hours straight.
To also get a time estimate
Free, no sign-up. Everything is computed in your browser: nothing you type here is sent anywhere.
How it is computed
First step, Kilian’s rule: 100 metres of climb cost roughly one flat kilometre. A 30 km with 1,500 m of gain is therefore worth 45 flat kilometres.
Second step, the terrain coefficient added on top: +8 % on rolling trail (under 20 m of gain per km), +15 % between 20 and 35, +22 % beyond, and 5 points more past 60 km. It covers what Kilian’s rule ignores: technical descents, scree, muscular fatigue.
The time estimate then applies your VMA to the flat-equivalent distance, and finally the coefficient. That is exactly the calculation Endu runs when judging a trail goal realistic or ambitious.
The plans built from this number
Now the plan that goes with it
These numbers are exactly the ones Endu uses to build a full preparation: phases, volume, detailed sessions, exported to your watch. 14-day trial, cancel any time.
Create my planFrequently asked questions
- Is the 100 m rule reliable?
- It is a good approximation on typical trail gradients, between 10 and 20 %. It under-estimates very steep slopes where you hike and the cost rises, and over-estimates gentle inclines you can almost run normally. The terrain coefficient absorbs part of that gap.
- What about descent?
- It is not counted as equivalent distance, because it costs almost nothing cardiovascularly. It is expensive muscularly, which is what the terrain coefficient reflects: on a very descending course, muscle damage arrives before breathlessness.
- How do I use it for my long runs?
- Think in duration and effort kilometres, never in raw distance. If your race is worth 45 effort kilometres, a long run at 25-30 effort kilometres in the specific phase is a sound marker, whatever the actual distance covered.
- Why is my estimated time faster than my actual time?
- The calculation assumes a cleanly run race, with matching training and short aid-station stops. On an ultra, the gap almost always comes from time spent standing still and from fuelling, not from physiology.