Free sleep calculators from the Yawnder review team. No sign-up, no email, nothing stored — every one of these runs in your browser and gives you a schedule you can actually act on tonight.
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Sleep cycle calculator
Enter the time you must wake up (or the time you are going to bed) and get bedtimes that land on the end of a sleep cycle instead of the middle of one.
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Sleep debt calculator
Log the last seven nights and see how many hours you are actually down — plus a realistic catch-up plan that will not wreck next week.
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Jet lag calculator
Tell us your flight direction and time-zone shift and get a day-by-day pre-travel plan so you land closer to local time.
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Kids’ bedtime calculator
Enter your child’s age and school wake-up time for a bedtime inside the recommended sleep range for that age group.
How to use these together
Most sleep complaints we hear on the showroom floor are a timing problem wearing a mattress costume. The order that works: find your real target sleep window with the sleep cycle calculator, check whether you are carrying a deficit with the sleep debt calculator, hold the schedule for two weeks, and only then judge whether your bed is the problem.
The math here is deliberately simple and it is the same math sleep clinicians use for schedule counselling: adult sleep runs in cycles of roughly 90 minutes (individually anywhere from about 80 to 110), and most people need about 15 minutes to actually fall asleep after lights out. Waking at the end of a cycle — in light sleep rather than deep sleep — is why two people who both slept seven hours can feel completely different in the morning.
Cycle length varies by person and by night, so treat every time below as a target to test for a week, not a prescription. Adults generally need 7–9 hours; consistently landing under 7 is where the measurable performance and health costs start.
What these calculators do not do
They are scheduling tools, not diagnostics. If you sleep a full night and still wake unrefreshed, snore heavily, gasp or stop breathing in your sleep, or fall asleep during the day, that pattern belongs in front of a doctor — no bedtime math will resolve sleep apnea, insomnia or restless legs. Nothing on this page is medical advice.
Once the schedule is right, the bed has to hold up its end
A calculator can fix your timing, but it cannot fix a mattress that traps heat, sags in the middle or wakes you every time your partner rolls over. If you are waking up sore or hot even on a sensible schedule, that is a hardware problem, not a scheduling one.
Not sure which bed fits you: use the mattress finder, compare specs side by side in the comparison tool, or read how we test.