Free trail & ultramarathon pace calculator
ROAD CALCULATORS LIEON THE MOUNTAIN.
A road pace calculator ignores 2,000 m of climbing. Enter your trail race distance, elevation gain and a recent 10K, and I'll estimate your real, elevation-adjusted finish time the way I do for my own athletes.
Made by Jonathan Fors, UESCA-certified ultrarunning coach. Top 5% on ITRA, elite field at MDS Legendary, 744 km across Portugal.
Your trail race finish time
Step 1 of 2
A real coach's method, not a generic formula.
I'm Jonathan, a UESCA-certified ultra coach. I've raced from the Sahara to 744 km across Portugal and I coach runners from their first half to 100 miles. This tool runs the exact rules I use when I set up an athlete's race day.
Vert counted as effort
Every 100 m of climbing costs about a kilometre of flat running. Descents cost too.
Terrain matters
Fire road, singletrack and technical scree each slow you down differently.
Long-race fatigue
Beyond the marathon your pace fades. The estimate plans for it instead of hoping.
Built for cutoffs
Know your buffer at every aid station before you start, not at km 60.
The record
THE TRACK RECORD OF YOUR COACH
- Top 5%
- Ranked worldwide on ITRA
- Elite runner
- Ranked as an elite runner in MDS Legendary 2025
- 744 km
- Longest run (Project Portugal)
Project Portugal · 1–10 August 2026
Most recently, I ran the entire coastline of Portugal, in 10 days, for men's mental health, with my partner Niki driving support. It was the second attempt. Two years earlier we set out on the same route and my immune system gave out at 480 km.
The second one is the line on the page. The first one is the reason it's worth anything: I know what it is to do the work, do it properly, and still have to stop — and then to decide whether you go back.
Enter your race and a few honest numbers
See your headline result instantly
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How do I calculate trail running pace with elevation?+
Count climbing as extra distance: roughly every 100 m of gain costs about a kilometre of flat running, and steep descents cost time too. The calculator does this for you, then adjusts for terrain and fatigue.
Is this a grade-adjusted pace calculator?+
Yes, for a whole race. It grade-adjusts your flat 10K fitness across the course's total climb and descent, instead of one hill at a time.
How do I predict my ultramarathon finish time?+
Start from a recent flat 10K, add the cost of the climbing and terrain, then allow for the slowdown past the marathon. That's exactly what the estimate does, shown as a range.
How accurate is it?+
It gives a range of about ±7%. Heat, night sections, altitude and fueling all move it, which is why the full plan includes split times you can adjust.
I don't have a recent 10K time.+
Use your best guess for a hard, flat 10K right now. If you're unsure, add a couple of minutes. Starting slower is safer.
Who made this calculator?+
Jonathan Fors, a UESCA-certified ultrarunning coach who races mountain ultras himself. It uses the same rules he uses to plan athletes' race days.
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