The format was born in 2011 in the United States, at Big's Backyard Ultra, held in Tennessee by Gary Cantrell, known as Lazarus Lake. It has since spread to many countries, on roads as well as trails. Its rule fits in one sentence, which is what makes it so easy for spectators to follow.
Where 4.167 miles comes from
The distance is no accident. 4.167 miles, or 6.706 km, is 100 miles divided by 24. A runner who completes 24 yards has run 100 miles, about 160.9 km, in exactly 24 hours. The yard count alone tells the distance covered.
| Yards completed | Distance | Race time |
|---|---|---|
| 1 | 4.2 miles, 6.7 km | 1 hour |
| 12 | 50 miles, 80.5 km | 12 hours |
| 24 | 100 miles, 160.9 km | 24 hours |
| 36 | 150 miles, 241.4 km | 36 hours |
| 48 | 200 miles, 321.9 km | 48 hours |
The hourly rule
Every hour, a bell starts the next loop. Runners must be in the start corral at that moment. Time on the loop is up to them, as long as they are back before the next start. Whatever is left of the hour is for drinking, eating, getting treated or sleeping a few minutes. A runner who does not finish the loop within the hour, or does not show up at the start, is out.
Last one standing
The race goes on as long as at least two runners start a loop. When only one is left, that runner still has to complete one more yard alone within the hour to win. If they do not, nobody wins. All other runners are ranked by the number of yards completed.
Variations chosen by race directors
The hourly rule does not change, but terrain and duration vary from one race to another. Each event's own rules are the reference.
A day course and a night course
Some races switch courses at nightfall, for example a trail by day and a road at night, always over the same distance. Big's Backyard Ultra works this way.
A capped duration
A backyard can set a maximum number of yards or an end time. The rules then say how runners still in the race on the last loop are ranked, for example as tied.
A shorter loop
For a beginner or kids' race, some race directors shorten the loop and the interval. The principle stays the same, but the distances no longer compare with a standard backyard.
Relays
Relay versions also exist, where a team shares the loops. Timing then follows the team rather than the runner.
Timing a backyard
Backyard timing counts yards more than it measures time. Every crossing of the line is timestamped, which shows who finished within the hour, and a second system backing up the line keeps a missed read from wrongly eliminating a runner. Live tracking is covered in the article following a backyard ultra live, and pricing on the backyard ultra timing page.
Frequently asked questions
- It is 100 miles divided by 24. Twenty four yards make 100 miles, about 160.9 km, in a day.
- As long as the last two runners hold on. The classic format has no set duration, only a variation can set an end time.
- Yes. No pace is required, all that counts is being back before the next start.
- Neither completed the extra yard alone, so there is no winner. Both are ranked with the same number of yards.
