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⏵ Course guide · Virginia ultra

Grindstone Trail Running Festival by UTMB Course Guide

Grindstone is Virginia’s flagship 100, now a UTMB World Series event, and it has a real reputation: a lot of people call it the toughest hundred east of the Mississippi. You get a 6 PM start, so you run the whole first night, roughly 21,000 feet of mountain climbing in the George Washington National Forest, and a 36 hour clock. I’ll walk you through the course first, then give you a pacing and fueling plan built for the climbing, the dark, and the long back half. There are free calculators along the way to dial in your own numbers.

⏵ At a glance

Grindstone by UTMB quick facts

Date
Festival Sep 17–20, 2026 · 100M starts Fri, Sep 18
Location
Natural Chimneys Park, Mount Solon, Augusta County, VA (George Washington National Forest)
Distances
100M (~104 mi) · 100K (~62 mi) · 50K · 21K
Elevation gain
100M: ~6,400 m (about 21,000 ft) · 100K: ~3,350 m (about 11,000 ft)
100M start
6:00 PM Friday (a night start by design)
Cutoff
100M: 36 hr · 100K: 18 hr · 50K: about 9 hr, with intermittent cutoffs
Qualifier
UTMB World Series (Running Stones, Finals access) and a Western States qualifier

These facts come from the official UTMB race site and UltraSignup. The course moved and changed when UTMB took it over, and dates, cutoffs, aid stations, and crew rules get adjusted year to year, so confirm the current race-day details before you commit.

The course: where Grindstone is won and lost

The 100 miler runs out from Natural Chimneys Park up into the George Washington National Forest, climbing the Allegheny and Great North Mountain ridges before working its way back, about 104 miles and roughly 21,000 feet of gain on mostly rugged single-track. It is an out-and-back in character, which means the climbs you grind up on the way out you get to face again, tired, on the way home. The shorter distances (100K, 50K, 21K) share the same mountains and the same kind of footing.

The first night: big climbs in the dark on fresh legs

You start at 6 PM, and within the first stretch the course throws you at the big climbs while it is getting dark. The long haul up toward Elliott Knob, one of the highest points in the area, is the kind of grind that sets the tone for the whole race. This is where Grindstone is quietly won or lost, because it feels easy in the cool evening air on fresh legs and it is so tempting to push. Hike the steep pitches efficiently, keep your effort honest, and let faster people go. The first night is a setup, not a race.

Run by headlamp the way you practiced, eat on a schedule even though you are not hungry in the dark, and stay on top of your layers as the ridges get cold. Get to sunrise with your legs and your stomach intact and you have done the single most important thing in this race.

The high ridges and the turnaround

Up high the course follows exposed ridgeline through the national forest, big climbs stacked one after another toward the far end of the route and the turnaround. The footing is rocky and rooty and sometimes technical, so quick feet and paying attention matter as much as raw fitness does, especially at night and again when you are deep into the second day and your focus is gone.

Because the race works back the way it came, the turnaround is a real mental checkpoint. Everything from here is the trip home, and the climbs you already paid for are waiting in reverse. Take stock at the turn: how are your feet, your stomach, your light situation. Fix the small problems there before they become the things that end your day.

The long way home: descents and the second-day lows

The back half is where Grindstone gets decided. Long descents on rocky single-track hammer quads that already have tens of thousands of feet of climbing in them, and the runners who blew the climb or never trained the downhills fall apart right here. If you saved something, the trip home is where you reel people in. If you did not, those final climbs and drops turn into a slow, grim shuffle.

For slower runners the clock pushes into a second night, and the low hours before a second sunrise are brutal: sleepy, cold, and full of doubt. This is exactly where a pacer and a good crew earn their keep, keeping you moving and eating when your own judgment has checked out. Practice controlled, runnable descending before race day so your legs still turn over downhill when they are cooked. That is honestly what separates finishers from DNFs out here.

Pacing strategy for a climbing-heavy night hundred

With roughly 21,000 feet of gain, a night start, and an out-and-back that makes you re-climb everything tired, Grindstone is about managing effort over a day-plus, not hitting a pace chart. Run the climbs by feel, especially that first night, and treat the descents as the real test of your legs.

Pace the climbs by grade, not by the watch

Your flat-ground pace means nothing on the long Grindstone climbs. What matters is grade-adjusted effort, so hold a steady output you can sustain up the grade and hike the steep pitches without feeling bad about it. The classic mistake here is running that first big climb too hard in the dark because the cool evening makes it feel easy, then paying for it on the descents and the back half. Use a grade-adjusted pace to turn your real fitness into honest climbing and descending targets, and you will not cook the front of the race.

Build a vert-aware finish prediction against 36 hours

Do not guess your Grindstone finish off a road or flat-ultra time. The 21,000 feet of climbing, the technical footing, the night, and the second-day fade all add real time. A vert-aware finish prediction that accounts for this course’s climbing gives you a realistic window and lets you work back into the 36 hour limit and the intermittent cutoffs, so you actually know how much buffer you have at each aid station instead of guessing in the dark at mile 70.

⏵ Free tools to pace this course

Fueling strategy for the distance and the night

You are out on the Grindstone 100 for the better part of a day and a night, maybe more, with long climbs and a full night of running. That makes carbohydrate, sodium, and fluid every bit as important as fitness, and it makes eating in the dark a skill you have to practice.

Carbs: steady, trained, and through the night

For an effort this long, aim for around 60 to 90 grams of carbohydrate per hour, and only push the higher end if your gut is trained for it. The hard part at Grindstone is not the math, it is staying on your intake at 2 AM when you are not hungry and everything tastes wrong. Keep your fuel easy to get down and stick to a schedule, because the calories you skip in the dark are the reason people fall apart at dawn. Rehearse your exact race-day carb rate on long runs, including some at night, so 80-plus grams an hour feels normal instead of like an experiment.

Sodium and fluid: cover the long climbs and the cold

Bias your sodium toward the high end, often around 500 to 700 milligrams per liter of fluid, and more if you are a heavy or salty sweater, especially through any warm, humid afternoon stretch. Carry enough fluid to get across the long climbs between aid stations instead of rationing to empty. The temperature swings a lot on this course, hot afternoon to genuinely cold ridge at night, so your sweat rate changes through the race. Weigh yourself before and after a long hot run to find your real number, then build the plan around it and adjust for the overnight cold.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the Grindstone distance with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.

⏵ Train for it with Summit Line

Get a race-day plan built around YOUR fitness, this exact Grindstone course profile, and your projected splits. Summit Line reads your real training, builds a plan for the climbing and the night, and rehearses your fueling so race day is something you execute, not guess at.

Start free →Explore the demo

Grindstone by UTMB FAQ

How hard is the Grindstone Trail Running Festival by UTMB?

Grindstone is widely called the toughest hundred east of the Mississippi, and that reputation is earned. The 100 miler covers about 104 miles with roughly 21,000 feet of climbing on mostly rugged single-track in the George Washington National Forest, and it starts at 6 PM, so you run the whole first night in the dark on fresh legs. The climbs are long and steep, the descents beat up your quads, and you are out there for up to 36 hours. It is not a fast East Coast hundred, it is a mountain hundred that happens to be in Virginia, and you should train it like one.

How much climbing is in the Grindstone 100?

The 100 miler has roughly 6,400 meters, about 21,000 feet, of total elevation gain across about 104 miles, per the official UTMB race materials, and because the course works back toward the start you descend a similar amount. The climbs are the kind that define the day: long grinds up the Allegheny and Great North Mountain ridges, including the big haul up toward Elliott Knob, one of the highest points around. The 100K is shorter at about 62 miles with roughly 11,000 feet of gain. Either way, this is a climbing race, so train the vert and train the downhills that come with it.

Why does Grindstone start at night, and how do I handle it?

The 6 PM Friday start is the signature of this race, and it is there on purpose: you hit the first big climbs in the dark with fresh legs, then run straight into the night before you have banked any sleep. Practice running by headlamp on real trail before race day, carry a bright primary light plus a backup and spare batteries, and resist the urge to chase faster runners early just because you feel good. The first night sets up your whole race. Run it controlled, keep eating in the dark even when you do not feel hungry, and you give yourself a body that still works at sunrise.

What are the cutoff times for Grindstone by UTMB?

The 100 miler has an overall limit of 36 hours, the 100K is a fairly aggressive 18 hours, and the 50K is around 9 hours, with intermittent cutoffs at points along the course so you cannot save all your buffer for the end. Thirty-six hours sounds generous, but with 21,000 feet of climbing, technical footing, and a full night (and into a second one for slower runners), the clock is real. Build your plan backward from the published aid-station cutoffs with margin, and confirm the exact intermediate times in the current race-day materials before you start.

Do I need crew, pacers, and drop bags for Grindstone?

For the 100 miler, yes, lean on all three. The course passes through crew-accessible aid stations where a good crew can refill your bottles, swap your gear, and get calories into you fast, and drop bags let you stash a headlamp battery, dry socks, and your preferred fuel at the points you cannot reach by car. A pacer for the back half is worth a lot here, because they keep you moving and eating through the second-night lows when your own judgment gets foggy. Check the current race rules for exactly which aid stations allow crew, pacers, and drop bags, because those details get adjusted year to year.

What is the terrain and weather like at Grindstone?

The course is mostly natural single-track (the race describes it as roughly 84% trail) with some gravel and fire road connecting the climbs, all in the George Washington National Forest west of the Shenandoah Valley. Expect rocky, rooty, sometimes technical footing, long sustained climbs and descents, and exposed ridgeline up high. Mid-to-late September in the Virginia mountains can swing a lot: warm or humid in the afternoon, then genuinely cold overnight up on the ridges, especially in the dark hours before dawn. Pack for both ends of that range and plan to add a layer at night.

This guide is independent and for planning only. The course details, dates, cutoffs, aid stations, and crew and pacer rules come from public sources and can change year to year, and the route was modified when UTMB took the race over, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.