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18 free calculators for bedtime, wake time, sleep debt, chronotype, and more. Built on sleep science, not guesswork.
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Sleep science explained
All articles →Sleep Science
Sleep Cycles Explained
What happens in each 90-minute cycle, and why waking mid-cycle feels terrible.
CircadianWhat Is a Chronotype?
Lion, Bear, Wolf, Dolphin, and the biology that determines which one you are.
Sleep ScienceCaffeine and Sleep
Caffeine's 5–7 hour half-life means your 2pm coffee is still 50% active at 9pm.
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Built on real sleep science.
Every calculator is built on peer-reviewed research and named consensus guidelines. See the methodology for the full source list.