90 Minute Timer — Fullscreen Flip Clock
Preset and ready — press start, no signup needed.
Ninety minutes matches the body's natural ultradian rhythm — a full cycle of high focus before energy naturally dips. It's the block researchers and peak-performers use for their most demanding, single-tasked work.
The clock is preset to 90:00 and starts on one click. Run it fullscreen and treat it as a "do not disturb" signal to yourself and everyone around you.
Tip: After a 90-minute block, take a real 20–30 minute break — walk, eat, or rest. Honoring the recovery is what makes the next cycle just as sharp.
Working with the ultradian cycle
- Start a ninety only when you are already rested. This is the one length where beginning tired guarantees you waste it — there is no recovering mid-block.
- Remove the interruption sources physically: phone in another room, door shut, notifications off at the system level. Ninety minutes is long enough that a single interruption will find you.
- Take twenty to thirty minutes afterwards, properly. Walk or eat; do not answer messages. The recovery is what makes a second cycle possible at all.
Ultradian rhythms run roughly ninety minutes from alert to dip, and one block rides a single wave. Most people manage two of these a day and no more — treating that as the ceiling rather than a personal failing is most of the skill.
Frequently asked questions
Why 90 minutes for deep work?
It aligns with the ultradian rhythm — roughly 90-minute cycles of alertness — so it fits one full wave of natural focus.
Can I pause if I get interrupted?
Yes, Pause holds the countdown and Start resumes it exactly where you stopped.
Is it free to use?
Yes, completely free and signup-free; a free account is optional for saving history.
Other timers
Timers by task
Looking for the Pomodoro cycle timer, meditation guides, or streak tracking? Open the full FlipFocus app.