Grindstone Trail Running Festival - 21K 2025
The forecast arrives five days before the start.
Here you'll find the elevation profile and an estimated finish time based on your UTMB Index.
What's your time based on your UTMB?
Times estimated by the RAVIT model, learned from real ultra-trail finish times. Enter your UTMB Index (utmb.world) to get a personalized estimate.
Cut-off times and crew - Grindstone Trail Running Festival - 21K · 2025
| Aid station | Cum. km | Cum. D+ | Seg. km | Seg. D+ | Seg. D- | Crew | Cut-off | Access |
|---|---|---|---|---|---|---|---|---|
| Lick Run - 1 | 7.5 | 0 m | 7.5 | 154 m | 28 m | — | — | — |
| Lick Run - 2 | 14.7 | 0 m | 7.3 | 300 m | 301 m | — | — | — |
| Natural Chimneys | 21.8 | 0 m | 7.1 | 30 m | 154 m | — | Sat 02:00 PM | — |
Data from the official race rules, checked for every edition. The race rules prevail. Positions are interpolated along the GPX track and are a guide, not official course marking.
What you'll find at each aid station
Aid station contents not documented.
La feuille de ton assistance pour Grindstone Trail Running Festival - 21K · 2025
Les règles d'assistance de cette course ne sont pas encore connues : tu marqueras tes rendez-vous toi-même.
Recto, verso et planche d'étiquettes, en PDF : l'exemple d'une coureuse de l'UTMB.
Elevation profile
The course and its aid stations
Grindstone Trail Running Festival - 21K: times, aid-station stops and fuelling needs by UTMB® Index
Between a UTMB® Index of 500 and 800, the estimated finish time on this race runs from 2h18 to 1h33, and the aid-station stop budget from 0h02 to 0h01. The longer the race, the more stops weigh: this is time you should plan to spend standing still, not only running.
Source
| UTMB® Index | Estimated time | Of which stops | Night hours | Carbs | Fluid | Sodium | Cut-off margin |
|---|---|---|---|---|---|---|---|
| 500 | 2h18 | 0h02 | — | 138 g | 1.6 L | 1,151 mg | +3h42 |
| 550 | 2h07 | 0h02 | — | 127 g | 1.5 L | 1,058 mg | +3h53 |
| 600 | 1h59 | 0h01 | — | 119 g | 1.4 L | 990 mg | +4h01 |
| 650 | 1h52 | 0h01 | — | 112 g | 1.3 L | 931 mg | +4h08 |
| 700 | 1h45 | 0h01 | — | 105 g | 1.2 L | 873 mg | +4h15 |
| 750 | 1h39 | 0h01 | — | 99 g | 1.2 L | 824 mg | +4h21 |
| 800 | 1h33 | 0h01 | — | 93 g | 1.1 L | 776 mg | +4h27 |
Figures based on 60 g of carbohydrate, 700 mL of fluid and 500 mg of sodium per hour, "average" preparation and mild conditions (15–25 °C). Above 25 °C, count on roughly 900 mL/h and 700 mg/h. Carbohydrate intake is trained: 60 g/h is a floor, 90 g/h assumes a glucose-fructose blend and a gut used to it.
Measured on the 2025 edition: the field checkpoint by checkpoint
135 starters, 1.5% DNF rate, 3 timed checkpoints.
| Segment | km | Median | Middle half | Measured | Median passage | Still ranked |
|---|---|---|---|---|---|---|
| Natural Chimneys → Lick Run - 1 | 7.5 | 50 min | 44 min – 57 min | 134 | 50 min | 134 |
| Lick Run - 1 → Lick Run - 2 | 14.7 | 1 h 09 | 1 h 00 – 1 h 22 | 132 | 2 h 00 | 133 |
| Lick Run - 2 → Natural Chimneys | 21.8 | 50 min | 43 min – 56 min | 133 | 2 h 51 | 133 |
“Median passage” is elapsed time from the start, not a clock time: the clock time depends on the edition.
Where runners drop out. Natural Chimneys (1) · Lick Run - 1 (1) out of 2 total DNFs.
RAVIT record from the official timing of the 2025 edition, data from September 16, 2026.
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Grindstone Trail Running Festival - 21K over the years
Sources and method
- Time projection — times by UTMB Index are taken from the actual splits of runners in each level band on previous editions of this race, aid station stops included. No formula is used as long as these results exist.
- Trail nutrition — hourly targets for carbohydrate, fluid and sodium follow the commonly accepted ultra-endurance guidance. La Clinique du Coureur — Fuelling in trail running
- Course, aid stations and cut-offs — taken from the event's official rules, which prevail in case of any discrepancy. Official site — Grindstone Trail Running Festival - 21K
Weather for Grindstone Trail Running Festival - 21K
The weather for Grindstone Trail Running Festival - 21K will appear here as soon as the forecast models reach that date, around five days before the start: feels-like temperature, rain, snow, wind and storms, section by section and at your passage time.
Detailed weather for Grindstone Trail Running Festival - 21K, hour by hour on the courseFrequently asked questions
How many checkpoints?
Grindstone Trail Running Festival - 21K has 3 checkpoints: 3 checkpoints with undocumented contents. Details are in the two tables above.
What distance and elevation gain?
Grindstone Trail Running Festival - 21K is 22 km long with 484 m of elevation gain.
How long to finish?
With a UTMB Index of 600 (average runner), the estimated time is around 1h59 for Grindstone Trail Running Festival - 21K.
What's the weather forecast?
The weather for Grindstone Trail Running Festival - 21K will be published on this page around five days before the start, once the forecast models reach the race date. It will be detailed section by section: feels-like temperature, rain, snow, wind and storms.
Want to stack the odds in your favor for Grindstone Trail Running Festival - 21K?
In 2 minutes, RAVIT generates your complete plan: segment-by-segment time, carbs, water and sodium at every aid station, printable roadbook.
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