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⏵ Course guide · Vermont ultra

Infinitus Course Guide

Infinitus is The Endurance Society’s cult loop race in the Green Mountains near Ripton, Vermont, and it is unlike almost anything else on the calendar. You run a muddy figure-eight of two loops over and over, and the distances run from a 9 mile all the way up to the 888K, about 551 miles and a full 10 days out there. I will walk you through how the loops actually run, then give you pacing, sleep, crew, and fueling strategy that fits a multi-day Vermont grind, plus free tools to dial in your own numbers.

⏵ At a glance

Infinitus quick facts

Date
Late May (festival runs about May 21 to 30, 2026)
Location
Silver Towers Camp, Ripton, VT, in the Green Mountain National Forest (Moosalamoo area)
Distances
9 mile, marathon, 88K, 100 mile, 250 mile, and the 888K (about 551 miles)
Course
Figure-eight of two loops: small loop about 8.5 mi / 2,090 ft, big loop about 17.8 mi / 2,760 ft
Elevation gain
888K totals roughly 84,000 to 100,000 ft across the full distance
Start
8:00 AM, on a staggered schedule by distance
Cutoff
888K 240 hr (10 days) · 250M 120 hr · 100M 48 hr · 88K 24 hr · marathon and 9 mile 12 hr
Qualifier
No Western States, Hardrock, or UTMB qualifier status listed by the race

These facts come from the official race site, UltraSignup, and race coverage. The exact start days, the loop distances, the vertical, and the cutoffs can change year to year, so confirm the current details with the race before you commit.

The course: where Infinitus is won and lost

Infinitus is not a point-to-point race with a finish line over the horizon. It is a figure-eight of two loops out of Silver Towers Camp in the Moosalamoo area of the Green Mountain National Forest, and you repeat them until you hit your distance. The small loop is about 8.5 miles with roughly 2,090 feet of gain, the big loop is about 17.8 miles with roughly 2,760 feet of gain, and both are rocky, rooty, and muddy the whole way. The 888K runner does this for about 551 miles and up to 10 days.

The loops: same trail, over and over

Every Infinitus distance is built out of the same two loops, so the course you face on lap one is the course you face on lap thirty. The small loop is the steep, leg-torching one: short but with sharp climbs that add up fast when you run it a dozen times. The big loop is the grind, longer and designed to wear you down in the back half of each section. You will get to know every rock, root, and mud pit by name, which is its own kind of mental test that a normal one-and-done race never gives you.

The footing is the headline here. This is heavily forested Vermont singletrack, and rocks, roots, and deep mud are a constant threat to your feet and ankles. It rarely lets you switch off and cruise. Quick feet, good ankle strength, and shoes you trust in slop matter as much as your aerobic engine, especially once you are tired and sloppy late in a loop.

The hub: the loop format is your biggest weapon

Because everything runs out of Silver Towers Camp, you pass back through the same central hub at the end of every loop. That makes Infinitus one of the most crewable monster ultras anywhere. Your crew, your drop bag, your dry socks, your spare shoes, your real food, and your sleeping spot are all in one place, and you hit them on a known interval. Smart runners turn that into a rhythm: come through, fix one thing, refuel, and get back out before the camp chair eats them alive.

Use this. On a point-to-point hundred you are stuck with whatever is in your pack between aid stations. Here you are never more than a loop from a full reset. The runners who do well treat each pass through camp like a quick, deliberate pit stop with a plan, not a random hangout.

The long game: feet, weather, and the back half

On the long Infinitus distances, the race is decided by what breaks down over days, not by your loop split. Feet are the number one thing that ends people’s races out here, because constant mud means constant wet, and wet plus miles equals macerated, blistered feet. A foot-care system and a shoe-and-sock rotation you actually use every few loops is not optional on the 250 mile or the 888K.

Then there is the Vermont weather, which in late May does whatever it wants. Infinitus has handed runners hot, humid days that dropped people with dehydration and then violent thunderstorms with the temperature crashing and real hypothermia risk, sometimes in the same race. Plan for both ends of that. The runners still moving on day eight are the ones who managed their feet, their layers, and their head, not the ones who were fastest on day one.

Pacing strategy for a multi-day loop ultra

Infinitus is not paced like a road race or even a normal hundred. With muddy, climby loops repeated for days, it is about a sustainable effort and a sleep plan, not hitting splits. Run by feel on the grade, and protect the days you have not run yet.

Pace by effort and grade, not by the clock

Your flat-ground pace means nothing on these loops. The steep small-loop climbs and the technical mud make grade-adjusted effort the only number worth watching, so settle into an output you could hold for far longer than feels necessary and hike the steep pitches without ego. The classic multi-day mistake is running early laps too fast because they feel easy, then falling apart on day three. Use a grade-adjusted pace to turn your real fitness into an honest, repeatable effort you can hold lap after lap.

Build a finish prediction, then plan the sleep around it

Do not guess your Infinitus time off a road result. The vert, the mud, the technical footing, and (on the long distances) the sleep you have to take all add huge amounts of time. A vert-aware finish prediction for your distance gives you a realistic moving-time window, and from there you can subtract planned sleep and figure out where you sit against the cutoff. On the 888K and 250 mile that math is the whole strategy: it tells you how much sleep you can afford and still beat the 240 or 120 hour limit.

⏵ Free tools to pace this course

Fueling strategy for a race measured in days

On the long Infinitus distances you are eating for days, not hours, and the loop hub gives you access to real food every lap. That makes a steady, gut-friendly fueling habit and good camp food just as important as your fitness.

Carbs: steady, trained, and topped up at camp

For the loop hours, aim for around 60 to 90 grams of carbohydrate per hour from gels, chews, and drink, and lean to the higher end only if your gut is trained for it. The difference at Infinitus is that you come through camp every loop, so you can layer in real food (soup, potatoes, a sandwich, whatever sits well) on top of your moving fuel. Over multiple days, appetite gets weird and sweet stuff stops going down, so plan a rotation of savory and salty options and keep eating even when you do not feel like it. The runners who keep fueling are the ones still moving on day eight.

Sodium and fluid: match it to the day’s weather

Vermont in late May swings hard, so your sodium and fluid plan has to swing with it. On the hot, humid days, bias sodium toward the high end (often 500 to 700 milligrams per liter of fluid, more if you are a salty sweater) and drink to your real sweat rate, because dehydration drops people here. On the cold, stormy stretches you will need less fluid but you still have to eat. Weigh yourself before and after a hard long run in advance to find your sweat rate, then carry enough between laps to cover the conditions on that lap, not yesterday’s.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the Vermont conditions 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 Infinitus loop profile, and your projected splits. Summit Line reads your real training, builds a plan for the vert and the mud, and rehearses your fueling so race day, or race week, is something you execute, not guess at.

Start free →Explore the demo

Infinitus FAQ

How hard is Infinitus?

Infinitus is about as hard as trail running gets, and the 888K is one of the longest trail events in the country at roughly 551 miles. The whole thing is a figure-eight of two loops in the muddy, rooty, rocky Moosalamoo terrain of the Green Mountains, and you just keep running them. The 888K stacks somewhere around 84,000 to 100,000 feet of climbing depending on whose number you trust, and you have a strict 240-hour (10-day) cutoff to get it done, which means managing sleep, your feet, and your head for over a week. Even the "short" Infinitus options are no joke: the marathon and the 88K run the same gnarly loops as everything else. So how hard it is depends entirely on which distance you sign up for, but none of them are easy, and the long ones are an expedition.

How long is the Infinitus 888K and how much climbing is in it?

The 888K is about 551 miles, run as a figure-eight of a small loop (around 8.5 miles with roughly 2,090 feet of gain) and a big loop (around 17.8 miles with roughly 2,760 feet of gain) that you repeat over and over. Public sources put the total climbing somewhere between roughly 84,000 and 100,000 feet across the full distance, so however you slice it, you are climbing the height of a few Everests on tired legs. The terrain is the real story though: rocks, roots, and deep mud the entire way. Confirm the current loop maps and the official vertical with the race before you build your plan, because the course and the numbers can shift year to year.

What are the Infinitus distances and cutoff times?

Infinitus is a festival of distances, all run on the same loops near Ripton. The lineup is a 9 mile, a marathon, an 88K, a 100 mile, a 250 mile, and the 888K, plus multi-day marathon challenges in some years. The cutoffs scale with the distance: the 888K gets 240 hours (10 days), the 250 mile gets 120 hours, the 100 mile gets 48 hours, the 88K gets 24 hours, and the marathon and 9 mile get 12 hours. The shorter races go off on the final Saturday and the long ones start earlier in the week, so the field is spread across the whole event. Always check the current schedule and cutoffs on the official site, since the exact start days move a little year to year.

What is the terrain and weather like at Infinitus?

The loops run through heavily forested Moosalamoo trail in the Green Mountains, and the footing is rocky, rooty, and famously muddy. This is not buffed, runnable singletrack: rocks, roots, and mud are a constant threat to your feet and ankles, and the steep climbs on the small loop are leg-torchers. Late-May weather in Vermont is volatile, and Infinitus has seen everything from hot, humid days that drop runners with dehydration to violent thunderstorms with the temperature crashing and hypothermia risk. Pack and plan for both ends of that range, because over a multi-day race you will probably get both.

How do you manage sleep, crew, and drop bags at Infinitus?

For the long Infinitus distances, sleep strategy is part of the race, not an afterthought. Because the course is a loop out of Silver Towers Camp, you come back through the same hub every lap, which makes it one of the most crewable big ultras out there: your crew, your drop bag, your dry shoes, and your bed are all in one place. Most 888K and 250 mile runners plan short, scheduled sleep blocks rather than pushing until they fall over, and they use the loop format to reset feet and kit every time through. Sort your foot care, your mud-shoe rotation, and your sleep plan in advance, and lean on that central camp hard. It is the biggest tactical advantage the course gives you.

Is Infinitus a good first ultra, or a Western States or UTMB qualifier?

The shorter Infinitus options (the 9 mile, the marathon, even the 88K) can be a great introduction to rugged Vermont trail running if you have done the work on technical, muddy terrain, but they are honestly hard for the distance because of the footing and the climbs. The 888K, 250 mile, and 100 mile are not first-ultra material: they are serious multi-day or all-day efforts that demand real ultra experience, crew, and a sleep plan. As for qualifiers, the race does not list Western States, Hardrock, or UTMB Running Stone status, so do not count on it for lottery entry. If you need a qualifier, confirm the current status directly with the race and the series before you register.

This guide is independent and for planning only. The course details, dates, loop distances, vertical, cutoffs, and aid come from public sources and can change year to year, so confirm the current specifics with The Endurance Society and the official Infinitus page before you register or run. The fueling and pacing advice is general and not medical advice.