Timed races look similar from the outside: run or walk as far as you can before the clock stops. Inside the race, 24-hour, 48-hour, and 6-day formats feel very different. The extra time changes pacing, sleep, foot care, food, emotions, and the meaning of a bad hour.
Quick Comparison
| Measure | 24-hour | 48-hour | 6-day |
|---|---|---|---|
| Clock length | 24 hours | 48 hours | 144 hours |
| Typical course | 400 m track or short certified loop | Short certified loop | Short loop, often a mile or less |
| Recorded performances, 2025 (DUV) | 16,685 | 2,462 | 553 |
| Reference race field | London 24-hour 2025, 52 results | 48 heures de Royan 2025, 38 results | EMU 6 Day World Trophy 2025, 37 results |
| Median distance in that field | 164.4 km | 201.1 km | 509.3 km |
| Middle 50% of that field | 136.7-183.2 km | 161.4-222.0 km | 345.6-599.6 km |
| Fastest result in that field | 242.9 km | 350.3 km | 805.7 km |
| World best, men (IAU) | 319.614 km, Sorokin, 2022 | 485.099 km, Bonne, 2025 | 1,045.519 km, Bonne, 2024 |
| World best, women (IAU) | 278.621 km, Webster, 2025 | 436.371 km, Bereznowska, 2025 | 928.577 km, Rex, 2025 |
| World best as average speed (men / women) | 13.3 / 11.6 km/h | 10.1 / 9.1 km/h | 7.3 / 6.4 km/h |
| Sleep planning | Plan rest access; do not require staying awake | Flexible sleep opportunities on both nights | Protected sleep every night; adjust to need |
| Crew and support norm | Optional; a table by the loop is usually enough | Useful; overnight kit and a rest place matter | Tent or cabin plus repeatable daily resupply |
| Training emphasis | Progressive easy volume and one long effort | Back-to-back days and a rehearsed rest routine | Repeated days, foot care, and walking volume |
The speed row is the clearest comparison in the table, and it is simple arithmetic: each world best divided by the clock length. The men’s figures fall from 13.3 km/h over 24 hours to 7.3 km/h over six days, a 45% drop in average speed, and the women’s from 11.6 km/h to 6.4 km/h. Six-day racing is not 24-hour racing repeated six times; it is a different speed entirely, because sleep, feet, and digestion have to be paid for out of the same clock.
The reference-race rows come from three complete result lists: all 52 results at the September 2025 Self-Transcendence London 24-hour, all 38 at the October 2025 48 heures de Royan, and all 37 at the September 2025 EMU 6 Day World Trophy. Field composition and goals differ: the Across the Years medians in December 2025 were 161 km for 48 hours and 328 km for six days. More fields are on the 48-hour and 6-day guides, and the London method is in the statistics report.
Entry fees vary too much by country and organizer for a single ballpark. As one sourced data point, the Self-Transcendence London 24-hour lists £120 for unaffiliated runners and £118 for UKA-affiliated club members, including lap counting, trackside refreshments, meals, and indoor changing facilities.
24-Hour Races
The 24-hour race on a short loop has the simplest logistics of the three. Our default is no planned sleep, with a short nap if you get drowsy; run/walk at 25 minutes running to 5 walking from the start; and a first target of 100 km if you have finished a marathon or 50K, or 130–160 km with a 100-mile finish behind you. Set the target lower if your training was interrupted.
Consider this format if the actual event offers straightforward travel, course marking, aid, and exit logistics. A 24-hour label alone does not guarantee a flat course, frequent support, or low gear needs.
48-Hour Races
A 48-hour race is not just a longer 24-hour race. Our default is 1–3 hours of sleep in total, mostly one block of about 90 minutes on the second night, with a nap on night one if you get drowsy; prepare for changes in fit and appetite on day two. Our first target is 160 km, which needs only 3.3 km/h averaged over the 48 hours.
Keep day one to about 55–60% of your target, so 90–95 km for 160 km.
6-Day Races
A 6-day race becomes a daily life problem. You are not only running. You are eating, sleeping, cleaning feet, changing shoes, managing swelling, keeping gear dry, and building a routine that can survive multiple bad patches.
Our first target is 400 km: 100–110 km on day one, then 55–65 km a day, with 2–4 hours of sleep every night from the first. Set the target lower if you have not yet finished a 48-hour race. The rhythm has to still work on day four, when the novelty is gone.
Training Differences
- 24-hour: 50–70 km a week at peak for a 100–130 km goal, a 4–5 hour long run, one back-to-back weekend and a 6–8 hour timed rehearsal on a loop.
- 48-hour: practice second-day movement and support within a load you already tolerate; test night kit at dusk while preserving normal sleep. The training guide uses a 4–6-hour rehearsal within the existing long-run allocation.
- Six-day: add 3–5 hours a week of brisk walking at 5–6 km/h, three-day training blocks, and foot-care practice on every long session.
See the training guides for 24-hour, 48-hour, and 6-day races for format-specific plans.
Which Should You Choose?
A progression from 24 hours to 48 hours and then six days can help you learn each system, but 150 km is not a validated entry requirement. Consider preparation, response to earlier events and support. Return to full training when symptoms, function and gradual easy activity support it; no fixed three-, five- or six-week deadline fits every runner.
Sources
- International Association of Ultrarunners - IAU world records and world best performances. 24-hour, 48-hour, and 6-day marks for men and women; page last updated May 6, 2026, checked October 23, 2026.
- DUV Ultramarathon Statistics - worldwide distance table, 2025. 24-hour 11,776 M + 4,909 F = 16,685; 48-hour 1,624 M + 838 F = 2,462; 6-day 386 M + 167 F = 553.
- Sri Chinmoy Marathon Team - Self-Transcendence London 24-hour 2025 official results and race information and entry fees.
- DUV Ultramarathon Statistics - 48 heures de Royan 2025 results, EMU 6 Day World Trophy 2025 results, and Across the Years 2025 48-hour and 6-day results. Medians and middle 50% calculated by us from every listed result on October 3, 2026.
- Multiday Running - 25 Multiday Running Statistics for 2026, where the London 24-hour median and percentile interval are calculated.
Frequently Asked Questions
Is a 48-hour race twice as hard as a 24-hour race?
Not by distance: the men's 48-hour record (485 km) is 76% of twice the 24-hour record (320 km). But it is a big step up. A 48-hour race adds another night, greater rest needs and more time for foot problems to develop.
Should you run a 24-hour race before a 6-day race?
Yes, we recommend it, ideally followed by a 48-hour race. Prior 24-hour experience can expose problems with pacing, food and feet through a night; no single distance proves readiness, and the 48-hour adds the planned sleep stops a six-day race repeats every night.
Which timed race format is best for beginners?
The 24-hour race, on a loop of 1–2 km. Aid comes every few minutes, there is no navigation, and you can stop at any point with a result. Our default first target is 100 km if you have finished a marathon or 50K; set it lower if your training was interrupted.