Ultradian rhythm work schedule

How the cycle schedule is built

The schedule repeats one unit: a focus block followed by a recovery break. The calculator places the first block at your start time, adds the block length to find when it ends, adds the break, and repeats for the number of cycles you choose. There is no break after the final block, so the finish time is start + cycles × focus + (cycles − 1) × recovery.

With the default values, starting at 9:00 with four cycles of 90 minutes and 20-minute breaks, the blocks run 9:00–10:30, 10:50–12:20, 12:40–14:10 and 14:30–16:00. That gives 6 hours of focused work and 1 hour of recovery, and the day of deep work ends at 16:00.

The idea comes from the sleep researcher Nathaniel Kleitman, who proposed a basic rest-activity cycle of roughly 90 minutes that runs through sleep and, he suggested, through waking hours as well. During sleep the cycle is well documented; the daytime version is less firmly established, so treat 90 minutes as a starting point rather than a fixed biological clock.

Making ultradian cycles work in practice

The signals that a block has run its course are familiar: rereading the same paragraph, reaching for your phone, fidgeting, a sudden urge for a snack. If they arrive reliably after 60 or 75 minutes, shorten the block in the calculator instead of pushing through. The recovery break works best when it is a real change: stand up, walk, look out of a window or get a drink. Scrolling messages keeps your attention busy and tends to leave you less refreshed.

Three or four full cycles are a realistic ceiling for demanding work such as writing, coding or analysis. Use the first cycles for the hardest task, because for many people concentration is strongest in the first hours of work, and leave email, meetings and admin for the time after your last block. A lunch break can replace one recovery slot: simply make that break 45 or 60 minutes and the rest of the schedule shifts later by the difference.