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Backyard ultra calculator
In a backyard ultra your distance is fixed and your rest is the variable. Everyone who is still in covers the same ground; the only thing your lap time buys you is the minutes before the next one starts.
Thirteen minutes a yard is a working margin — enough to change, eat and lie down for a few minutes.
What each lap time buys you
For the standard 6.706 km (4.167 mile) yard on an hourly cut-off. Twenty-four yards is 100 miles, whatever your lap time — the last two columns are the whole trade.
| Lap | Rest | min/km | min/mile | On your feet | Off them |
|---|---|---|---|---|---|
| 40:00 | 20:00 | 5:58 | 9:36 | 16h 00m | 8h 00m |
| 42:00 | 18:00 | 6:16 | 10:05 | 16h 48m | 7h 12m |
| 44:00 | 16:00 | 6:34 | 10:34 | 17h 36m | 6h 24m |
| 46:00 | 14:00 | 6:52 | 11:02 | 18h 24m | 5h 36m |
| 48:00 | 12:00 | 7:09 | 11:31 | 19h 12m | 4h 48m |
| 50:00 | 10:00 | 7:27 | 12:00 | 20h 00m | 4h 00m |
| 52:00 | 8:00 | 7:45 | 12:29 | 20h 48m | 3h 12m |
| 54:00 | 6:00 | 8:03 | 12:58 | 21h 36m | 2h 24m |
| 56:00 | 4:00 | 8:21 | 13:26 | 22h 24m | 1h 36m |
| 58:00 | 2:00 | 8:39 | 13:55 | 23h 12m | 0h 48m |
The rest column is not really rest. It has to absorb getting to the tent, changing anything wet, eating, any medical attention, and being back in the pen before the whistle. Backyard Ultra Live warns you below five minutes of projected buffer by default, because five minutes is roughly the point at which a yard stops having any slack in it at all.
How to read the numbers
Rest compounds, distance doesn't
Running a 44 rather than a 50 does not put you further ahead — you both start the next yard together. It buys six minutes, every hour, and by hour twenty that difference is measured in sleep.
Your first lap sets a trap
The pace that feels absurdly easy in daylight is the pace you have to hold at 4 a.m. in the rain. Pick the lap time you could repeat while miserable, not the one you can run now.
The cut-off is not always an hour
Most backyards run hourly, but the format only requires a fixed period. Change the cut-off field and the whole table moves with it.
Backyard Ultra Live does this arithmetic continuously while you run, against your actual position on the loop — see how the two bars work, or read what a backyard ultra actually is.