The 90/30 ultradian deep work timer

The 90/30 interval follows the body's ultradian rhythm — natural cycles of roughly 90 minutes of high alertness followed by a dip that demands real recovery. Instead of fighting the dip with caffeine, this rhythm schedules around it.

Ninety minutes is enough to enter and stay in a genuine flow state, which makes this the interval of choice for research, complex creative work, and hard engineering problems. The 30 minute break is non-negotiable: walk, eat, nap — anything but another screen.

Two or three of these cycles is a world-class deep work day. Your garden will show it: each session plants 90 minutes of growth.