Grindstone by UTMB - 100 Mile

Grindstone 100M Finish Time Predictor

Grindstone 100M race stats pre-loaded (167.4 km, 6,400 m D+). Enter a known race result to get an elevation-adjusted finish time estimate.

167.4km6,400m D+Winner: ~21h48Cutoff: 36h

Full Grindstone by UTMB - 100 Mile course data: aid stations, cutoffs, course profile

1. Your race

Grindstone 100M

167.4 km · 6400 m D+ · 6402 m D-

Different race?

Have the GPX? Measure the exact course in the GPX Explorer

2. How should we estimate you?

From my Strava historyYour last 90 days of real training. Opens the TrailMath app.Read-only access to your activities. Nothing is posted to Strava, and no training plan is created until you ask for one.

Distance (km)

Elevation gain (m)

Elevation loss (m)

Same as gain. Edit if different.

Finish time

Hours, or h:mm

3. Your predicted finish

231.4 km-effort (ITRA, gain only)263.4 km-effort

Add a past race or your index to get a finish time.

Grindstone 100M finish times by UTMB Index

Predicted finish on the Grindstone 100M course (167.4 km, 6,400 m D+) for each UTMB Index, with the margin to the 36h00 cutoff.

Grindstone 100M: predicted finish time by UTMB Index
UTMB Index	Predicted finish	Average pace	Margin to cutoff
850	17h13	6:10 /km	+18h47
800	18h49	6:45 /km	+17h11
750	20h34	7:22 /km	+15h26
700competitive	22h29	8:03 /km	+13h31
650	24h34	8:48 /km	+11h26
600	26h52	9:38 /km	+9h08
550	29h22	10:31 /km	+6h38
500mid-pack	32h06	11:30 /km	+3h54
450	35h05	12:34 /km	+0h55
400back of the pack	38h21	13:45 /km	2h21 past the cutoff
350	41h55	15:01 /km	5h55 past the cutoff
300	45h49	16:25 /km	9h49 past the cutoff

The 36h00 cutoff sits at about Index 436. The typical winning time, 21h48, sits at about Index 717. A model estimate, not an official ITRA or UTMB figure.

From a result you already have

What the predictor gives on Grindstone 100M for a few common reference results.

Grindstone 100M: predicted finish from reference results
Road marathon	3h00 → 28h15	3h30 → 32h58	4h00 → 37h41	4h30 → 42h23
50 km trail, 2,000 m D+	5h30 → 23h40	6h30 → 27h59	7h30 → 32h16	8h30 → 36h33

Road marathons use the tool's rougher power-law fallback.

For arrival times at each checkpoint, use the Grindstone 100M aid station planner.

Grindstone 100M course in numbers

Climbing per km: 38 m
ITRA km-effort: 231 (100M)
Highest point: 1,323 m
Biggest climb: +758 m over 13.6 km at 4.1% (through Lookout Mountain)
Steepest climb: +538 m over 5.5 km at 9.5%
Longest descent: -434 m over 11.6 km at 2.8% (down to Natural Chimneys (Finish))
Track climbing above 3%: 36%
Winning time / cutoff: 21h48 / 36h00 (1.7x the winner's time)

Section-by-section climbs, descents and grades are on the Grindstone 100M course page.

Predict your Grindstone 100M finish time from a reference race result, adjusted for the course's 167.4 km and roughly 6,400 m of elevation gain. The overall cutoff is 36h.

About Grindstone by UTMB - 100 Mile

Grindstone by UTMB - 100 Mile covers 167.4 km (about 104 miles) with around 6,400 m of elevation gain, starting in Natural Chimneys Park, Virginia, USA. The overall cutoff is 36 hours.

Crew access is allowed at North River Gap 1 (52.1 km), Dowells Draft 1 (73.4 km), Dowells Draft 2 (115.7 km), Camp Todd (132.1 km) and North River Gap 2 (147.7 km). Drop bags are available at North River Gap 1, Dowells Draft 1, Dowells Draft 2, Camp Todd and North River Gap 2.

Checkpoint data approximate - verify against the current official race guide at grindstone.utmb.world before your race.

How the prediction works

Your result becomes a UTMB Index, mapped onto Grindstone 100M by the calibrated model behind the ITRA / UTMB Index Estimator. Full methodology.

Build a training plan targeted at your Grindstone 100M goal time

TrailMath uses these models to build periodized plans adjusted to your goals and terrain.

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