One hundred miles, many course models
100-Mile Ultramarathons
A fixed-distance ultramarathon where terrain, cutoff structure, night running, aid access, and crew rules can matter as much as the 100-mile label.
Cover photo: Jametlene Reskp / Unsplash
How the Format Works
A 100-mile ultramarathon covers approximately 160.9 kilometers, but the shared distance does not make every race operationally similar. A flat loop, a mountain point-to-point course, and a remote technical trail can demand very different pacing, equipment, support, and time on feet.
Most runners will encounter darkness, cumulative foot and stomach problems, changing temperatures, and hard cutoff decisions. The useful comparison is therefore not just distance: study the course model, climbing, aid gaps, crew and pacer access, mandatory gear, intermediate cutoffs, and withdrawal logistics for the exact edition.
Curated preparation path
Learn, Train, and Plan
1. Choose the Right 100-Miler
Match terrain, support, cutoff structure, and expected duration to your experience rather than choosing by reputation alone.
How to Choose Your First Multiday Race
Compare logistics, terrain, duration, support, and personal readiness before committing.
AnswerBest First Ultramarathon Distance
Use readiness and course demands rather than assuming one first distance suits everyone.
GuideUS 100-Mile Race Directory
Compare source-checked races by date, state, terrain, course model, and cutoff.
2. Build Durable Movement
Prepare to alternate efficient running and hiking while protecting enough capacity for the final miles.
Walking Strategy for Ultramarathons
Plan purposeful hiking before fatigue turns every walk break into an emergency response.
AnswerHow Long Does Ultramarathon Training Take?
Build a readiness timeline from current consistency, recovery, and race-specific demands.
GuideTapering for Ultramarathons
Reduce fatigue without trying to add last-minute fitness or unfamiliar routines.
3. Plan Aid, Fuel, and the Night
Rehearse the decisions that become harder when pace slows and darkness changes the course.
Crew and Aid-Station Strategy
Build efficient stops around the access and assistance the race actually allows.
GuideGut Training for Ultrarunners
Practice familiar foods, portions, timing, and fallback options before race week.
Gear guideHeadlamp and Battery Strategy
Match lighting, backup power, and beam choice to the route and expected hours of darkness.
4. Protect Feet and Decision Quality
Use practiced systems for friction, shoe changes, symptoms, and late-race judgment.
Blister Prevention
Reduce moisture, friction, pressure, and fit problems before they compound.
Gear guideFoot-Care Kit for Multiday Running
Prepare a small, tested response kit rather than improvising after damage develops.
ToolInteractive Gear Checklist
Build a personal list, then reconcile it with the current mandatory-kit rules.
Curated race directory
Selected Upcoming 100-Mile Races
21 matching events as of Oct 13, 2026; event source reviews dated August 10, 2026 – October 12, 2026. 19 past editions remain in the directory archive.
Ghost Train 30-Hour Ultramarathon
Camp Tevya, Brookline, New Hampshire, USA
A 30-hour race on the Granite Town Rail Trail between Brookline and Milford. Runners may stop after any completed 15-mile out-and-back; 100 miles takes six full laps plus a 10-mile seventh, and some keep going.
View verified race details →Gila 100
Santa Clara, near Silver City, New Mexico, USA
A 100-mile race in the Gila National Forest that covers the 50-mile out-and-back from Santa Clara to Sapillo Campground twice, following the Continental Divide Trail to nearly 9,000 ft, with roughly 14,774 ft of climbing and a 36-hour limit.
View verified race details →Sonoma Fall Classic 100 Mile
Lake Sonoma, Geyserville, California, USA
A new 100.5-mile, two-loop race at Lake Sonoma, with an estimated 25,058 ft of climbing and a 36-hour limit.
View verified race details →Uwharrie 100 Mile Trail Run
Uwharrie National Forest, near Troy, North Carolina, USA
Five laps of a technical 20.5-mile figure-eight loop of rocky, rooty singletrack in North Carolina's Uwharrie National Forest, 102.5 miles in all with 17,420 ft of climbing and a 36-hour limit.
View verified race details →Cactus Rose 100 Mile
Hill Country State Natural Area, Bandera, Texas, USA
Four 25-mile loops of rocky Hill Country trail near Bandera, alternating direction each lap, with unstaffed aid stations that supply only water and ice and a 44-hour limit.
View verified race details →No Business 100
Pickett CCC Memorial State Park, Jamestown, Tennessee, USA
A single 100.2-mile loop from Pickett CCC Memorial State Park through the Big South Fork into Kentucky and back, run counterclockwise in 2026, with about 14,500 ft of climbing and a 34-hour limit.
View verified race details →Showing the next 6 races here; use the full directory for all 21 active or upcoming records. Dates, entry status, routes, and rules can change. Use each event page's official organizer links before registration or travel. Format preparation paths were reviewed August 10, 2026.
100-Mile FAQs
How far is a 100-mile ultramarathon in kilometers?
One hundred miles is approximately 160.9 kilometers. The organizer's measured course may be slightly longer or use a named 100-mile category, so check the published exact distance.
What is a typical 100-mile race cutoff?
Most 100-mile trail races allow 30–36 hours. Western States and Leadville allow 30 hours, UTMB (about 175 km) 46 hours 30 minutes, and Hardrock, with over 10,000 m of climbing, 48 hours. Check the intermediate aid-station cutoffs too, because missing any one of them ends your race.
Is a 100-mile race the same as a 24-hour race?
No. A 100-mile race ends when the runner completes the course inside its cutoffs; a 24-hour race scores how much distance the runner covers before a fixed clock expires. Some festivals offer both options on one course.
Compare Related Formats
Fixed-Distance Multiday Races
A broad family of continuous races where the finish line is fixed but the distance, duration, terrain, and support model vary widely.
24-Hour Races
A fixed-time race where the clock runs for one full day and every completed lap or measured distance counts.
200+ Mile Races
A continuous fixed-distance ultramarathon where route, terrain, sleep, aid access, and a multi-day cutoff shape the race.