About

Calmer nights, sharper mornings.

The Sleep Time Calculator is a free, ad-light tool built on a simple idea: a well-timed alarm, not just enough hours, is what makes the difference between waking up groggy and waking up sharp.

What we do

We translate the 90-minute sleep cycle model into practical times you can set tonight. Enter when you want to wake up (or go to bed), pick your age band, and the calculator surfaces cycle-aligned windows so your alarm catches you in lighter sleep, not the depths of slow-wave sleep.

How we approach the science

Every calculation is based on peer-reviewed research. We cite the National Sleep Foundation's expert duration consensus (Hirshkowitz et al., Sleep Health, 2015), the foundational sleep-stage work of Aserinsky & Kleitman and Dement & Kleitman, and contemporary reviews from the American Academy of Sleep Medicine. See our methodology for the exact formulas.

What we don't do

We don't diagnose, prescribe, or replace medical advice. If you have persistent insomnia, suspected sleep apnea, or other sleep concerns, please see a licensed healthcare provider, preferably a board-certified sleep medicine specialist.

Privacy

Calculator inputs never leave your browser. We use anonymous analytics only. See our privacy policy for details.