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⏵ Course guide · Idaho ultra

IMTUF 100 Course Guide

The IMTUF 100, short for the Idaho Mountain Trail Ultra Festival, is Idaho’s flagship mountain 100 and one of the toughest in the West. It is a big loop out of Jug Mountain Ranch near McCall through the Salmon River Mountains, about 22,000 feet of climbing over 8 high passes, with a long remote night, technical footing, and a finish rate that humbles people. I will walk you through the course first, then give you a pacing, fueling, and crew plan built for exactly this kind of day, plus free tools to dial in your own numbers.

⏵ Quick facts

IMTUF 100 at a glance

Date
Sep 19 to 20, 2026 (15th annual)
Location
Salmon River and West Central Mountains, near McCall, ID
Start / Finish
Jug Mountain Ranch (loop course)
Distances
100 miles · 20 miles (Jughandle)
Elevation gain
About 22,000 ft, over 8 high passes
100 mile start
Saturday, 6:00 AM
Cutoff
36 hours (finish by about 6:00 PM Sunday), with aid-station cutoffs
Qualifier
Hardrock 100 qualifier and Western States 100 qualifier

These facts come from the official IMTUF race site and UltraSignup. The course, aid stations, exact splits, cutoffs, and crew and pacer rules can shift year to year, so confirm the current details with the race before you commit. The 100 miler is a hot ticket and often fills.

The course: where IMTUF is won and lost

IMTUF is a roughly 100 mile loop that starts and finishes at Jug Mountain Ranch and tours the high country of the Salmon River and West Central Mountains. Around 22,000 feet of climbing, 8 high passes, lakes, deep timber, and steep rocky singletrack for most of it. The low point sits near the ranch around 5,200 feet and the passes climb toward 8,000. This is not a course you out-run. It is a course you out-last.

The early miles: bank patience, not time

You roll out of Jug Mountain Ranch at 6:00 AM and the climbing starts early. The first big push heads up toward the high lakes country, and it is tempting to feel great on fresh legs in the cool morning and press. Do not. The smartest thing you can do in the first quarter of this race is give time back on purpose: hike the steep stuff, keep your effort boringly even, eat from the very start. There is so much mountain ahead that any time you bank early on tired legs gets paid back with interest somewhere on a pass in the dark.

Through the first chunk you tick off alpine lakes and ridgelines, and a couple of the early aid stations are road-accessible, so this is where your crew gets eyes on you before the course swallows you into the backcountry. Use those early stops to lock in your fueling rhythm and check your kit, because the gaps only get longer and lonelier from here.

The remote middle: the long night, alone

This is the heart of IMTUF and where it earns its reputation. There is a long stretch, on the order of 30 miles, where you get no crew and no pacer while the sun sets and you cross the most isolated terrain on the course. The distances between aid stations stretch out, and for a mid-pack runner it can be hours, four hours and then another four, between stops in the dark. You are out there by yourself, on technical trail, with your headlamp and your own head.

Plan for this section like a survival leg. Carry enough light, layers, calories, and water to be fully self-sufficient for hours. The Idaho high country gets cold overnight, sometimes near freezing up on the passes, so the layer you stuff in your pack at sundown is the one that keeps you moving at 2 AM. The runners who handle this part calmly, who keep eating and keep their feet moving when there is no aid station and no company for a long time, are the ones still in it at dawn.

The back-half climbs: Snowslide and Boulder Mountain

IMTUF saves its meanest climbs for when you are already cooked. The Snowslide climb is about as steep as they come, roughly 17 percent average grade up to the summit, and then later Boulder Mountain stacks something like 2,400 feet over about 3.4 miles. Both land deep in the back half, well past the point where your quads and your patience are fresh. People go a little delirious on Boulder. That is normal here.

There is no trick to these except preparation and a calm head. Get your poles out, shorten your stride, lock into a hike you can repeat forever, and eat on the climb even when you do not want to. Break the ascent into chunks between switchbacks or landmarks. The summit comes eventually, and getting over the last big passes with your mind intact is most of the battle this late in the race.

Footing, descents, and the run back to the ranch

Call it 85 percent singletrack, with the rest a mix of rough rocky forest road and a little smooth dirt. Plenty of it is technical: loose rock, roots, off-camber trail, the kind of footing that punishes tired feet and a wandering mind. The descents are steep and rocky, and after a full day and night of pounding they will find every weakness in your quads and your downhill technique.

The closing miles drop you back toward Jug Mountain Ranch and the finish. If you paced the early climbs with discipline, protected your legs on the descents, and kept eating through the night, you get to actually run some of the end. If you went out hot or skipped the downhill training, the last stretch turns into a long, careful shuffle. Either way, finishing IMTUF means you beat a course that turns away around half the people who start it.

Pacing strategy for a high-vert, remote 100

With 22,000 feet of climbing, 8 passes, and a long unsupported night, IMTUF rewards patience, hiking efficiency, and a head that stays calm alone in the dark. Run this one by effort, not by any pace chart.

Pace the climbs by grade, not the watch

Your flat-ground pace is meaningless on a 17 percent grade up Snowslide. What matters here is grade-adjusted effort: hold a steady, sustainable output up every climb and hike the steep pitches without a second thought, because almost everyone hikes the steep stuff at IMTUF. The classic blow-up is pushing the early climbs because they feel fine, then having nothing left for Boulder Mountain in the dark. Use a grade-adjusted pace to turn your real fitness into honest climbing and descending targets, and you will not torch the first half.

Build a vert-aware finish prediction against the 36 hour clock

Do not guess your IMTUF finish off a road 100 or a mellow trail race. The 22,000 feet of gain, the technical footing, and the slow remote night all add real time. A vert-aware finish prediction built on this course’s climbing gives you a realistic window, and then you can work backward into the aid-station cutoffs so you know how much buffer you actually have at each one. The 36 hour limit is generous on paper, but the terrain eats hours, so plan against the intermediate cutoffs, not just the final clock.

⏵ Free tools to pace this course

Fueling strategy for a full night (and then some)

Most finishers are out on the IMTUF course for somewhere in the 24 to 36 hour range, through cold nights and long gaps with no aid. That makes a steady, trained gut and self-sufficient drop bags matter as much as fitness.

Carbs: steady, trained, and protected through the night

For an effort this long, aim for roughly 60 to 90 grams of carbohydrate per hour, and only push the high end if your gut is genuinely trained for it. The real challenge at IMTUF is not the daytime, it is keeping fuel going down through the cold, lonely night hours when your appetite vanishes and the next aid is hours away. Practice eating on long, late, tired runs so a steady hourly carb number feels automatic, not like a decision you have to make at 3 AM. The day you stop eating out here is the day the wheels come off.

Sodium, fluid, and self-sufficient drop bags

Bias your sodium to your own sweat rate, often somewhere around 300 to 700 milligrams per liter of fluid, more if you run salty, and weigh yourself before and after a long training run to find your real number. The bigger logistical piece at IMTUF is the long unsupported gaps: carry enough fluid and calories to cover hours between aid stations instead of rationing to a stop that is still a pass away.

Pack your drop bags so you can run those remote legs fully self-contained. Lights and spare batteries, warm layers for the cold passes, the calories your stomach still tolerates late, and backups for anything that breaks. Confirm the current drop-bag list and crew points with the race, then build each bag around the leg it has to get you through.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the IMTUF night 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 IMTUF course profile, and your projected splits. Summit Line reads your real training, builds a plan for the climbing and the long night, and rehearses your fueling so race day is something you execute, not guess at.

Start free →Explore the demo

IMTUF 100 FAQ

How hard is the IMTUF 100 (Idaho Mountain Trail Ultra Festival)?

It is one of the harder mountain 100s in the West, and it is not shy about it. You loop roughly 100 miles out of Jug Mountain Ranch through the Salmon River Mountains with about 22,000 feet of climbing over 8 high passes, most of it on rugged, rocky singletrack with a few horrible stretches of forest road thrown in. The climbs are long and steep, the descents are technical, and big chunks of the course are genuinely remote with no crew and no pacer for hours at a time. The finish rate tells the story: it is common for around half the field to not make it to the line. The race even bills itself as a post-doctoral level mountain event, and that is fair. This is a Hardrock and Western States qualifier for a reason.

How much climbing is in the IMTUF 100?

Around 22,000 feet of total gain across the 100 mile loop, spread over 8 high passes, with the low point near Jug Mountain Ranch around 5,200 feet and the high passes pushing close to 8,000 feet. It is not one giant climb, it is climb after climb after climb, and the worst of it tends to come late. The Snowslide climb runs roughly 17 percent average grade, and Boulder Mountain stacks something like 2,400 feet over about 3.4 miles, both deep into the back half when your legs are already wrecked. Plan to hike a lot of vertical, and train your uphill hiking like it is a real skill, because here it is.

What are the cutoff times for the IMTUF 100?

The overall limit is 36 hours, so you have from the Saturday 6:00 AM start until roughly 6:00 PM Sunday to get an official finish, with intermediate cutoffs at aid stations along the way. That sounds generous compared to a 30 hour race, and it has to be, because the terrain is slow and the nights are long. Do not let the big number fool you into starting careless. The aid-station cutoffs and the sheer difficulty of the climbing late in the race are what actually end most days, not the final clock. Confirm the current cutoff chart with the race before you build your plan.

What is the terrain and weather like at the IMTUF 100?

Rugged mountain singletrack is the headline, something like 85 percent of the course, with the rest split between rough rocky forest roads and a little smooth dirt. Expect steep climbs, technical rocky descents, high alpine passes, deep timber, lakes, and a few spots where the trail is more of a suggestion. Mid-September in the Idaho high country can swing hard: warm and dry in the afternoon sun, then genuinely cold up on the passes overnight, sometimes near or below freezing. Pack for both ends of that range and respect the night, because you will be out for one full night and likely into the next one.

Where can crew and pacers meet me at the IMTUF 100, and can I use drop bags?

Crew and pacers can reach you at a handful of road-accessible aid stations, the kind of trailhead and campground spots like Upper Payette Lake, Snowslide, and others, but big sections in between are deep in the backcountry with no access at all. There is a long remote stretch, on the order of 30 miles, where you get no crew and no pacer while the sun goes down and you cross the most isolated terrain on the course. Drop bags go to the designated aid stations, so pack them so you can run self-sufficient through those gaps: lights, layers, calories, and whatever your stomach will still take in the dark. Confirm the current pacer and crew rules and the drop-bag list with the race, since they tweak it year to year.

Is the IMTUF 100 a good first 100 miler?

Honestly, for most people, no. IMTUF is a brutal place to attempt your first 100 given the vert, the technical footing, the remoteness, and the high DNF rate. If you have already finished a mountain 100 and you want a real test, it is a fantastic, beautiful, savage objective and a strong Hardrock qualifier. If it is your first hundred, you want serious time on technical climbs and descents, a fueling and night-running plan you have rehearsed, and the experience to keep moving alone for hours when it gets hard. Build that base first, then come get humbled by Idaho on purpose.

This guide is independent and for planning and training only. The course details, dates, cutoffs, aid stations, and crew and pacer rules for the IMTUF 100 come from public sources and can change year to year, 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.