90 Minute Timer

Ninety minutes aligns perfectly with the body's ultradian rhythm — the natural cycle of peak focus and recovery that repeats throughout the day. Sleep researcher Nathaniel Kleitman found that we oscillate between roughly 90 minutes of high alertness and 20 minutes of lower energy. It's also the length of a feature film, a full football match half-time to half-time, and many university lecture slots. Use this timer for deep creative work, marathon study sessions, or long baking projects. The countdown stays precise even in background tabs, and a clear alarm sounds when time's up.