90 Minute Timer for Deep Work

A free 90 minute timer for long, deep work sessions — the longest interval this timer supports, and for good reason. Press play, disappear into one hard problem, and let the chime tell you when the block is over.

The science of the 90 minute block

Sleep researcher Nathaniel Kleitman found that the human body cycles through roughly 90 minute rhythms — not just at night, but during the day too: about an hour and a half of higher alertness followed by a dip. Performance researchers later noticed the same shape in elite musicians and athletes, who tend to practice in concentrated sessions of about 90 minutes with real rest between them. A 90 minute timer simply works with that rhythm instead of against it.

How to use a deep work block

• Reserve 90 minute blocks for your hardest, most valuable work — not email.
• Two, at most three, blocks per day is realistic. Elite performers rarely sustain more.
• Take a genuine 20–30 minute break afterwards: walk, eat, rest your eyes.
• Protect the block — phone in another room, notifications off, and the timer popped out and always on top so the commitment stays visible.

Frequently asked questions

Is 90 minutes too long to focus?

For shallow tasks, yes — use a 25 minute timer for those. Ninety minutes earns its keep on deep work, where the first twenty minutes just load the problem into your head and stopping early throws that investment away.

How many 90 minute sessions per day?

Two or three. Beyond that, quality collapses quietly — you sit there longer but produce less. Finish your blocks, then do shallow work or stop.