Sleep Calculator
Find the best bedtimes or wake times using 90-minute sleep cycles, plus a sleep-debt check.
Best times
90-minute cyclesRecommended times
Sleep debt check
Personalised guidance
How to use the Sleep Calculator
Step 1 — Enter your details
- Add your measurements and pick your options.
Step 2 — Read the dashboard
- Results, gauge and breakdown update instantly.
Step 3 — Explore the detail
- Review the per-method figures and personalised guidance.
Step 4 — Export
- Download a PDF report or print it.
Frequently asked questions
Sleep runs in cycles of roughly 90 minutes. Waking at the end of a cycle, rather than mid-cycle, tends to feel more refreshing, so the tool suggests bed or wake times that fall on whole-cycle boundaries (plus time to fall asleep).
Most adults do well on 5–6 cycles, about 7.5–9 hours. The tool highlights these but shows shorter options for naps or short nights too.
No — it is an average. Real cycles range from about 70 to 120 minutes and vary night to night, so treat the times as helpful targets rather than precise guarantees.
The gap between the sleep you need and what you actually get, accumulated over time. The tool compares your average to the age-based recommendation and estimates your weekly shortfall.
If you regularly sleep poorly, snore loudly, gasp in your sleep, or feel exhausted in the day despite enough hours, those are worth discussing with a doctor. This tool gives general information for education, not medical or dietetic advice; consult a qualified professional for guidance about your health.
About the Sleep Calculator
This tool helps you wake up feeling refreshed by timing your sleep around natural ~90-minute cycles. Tell it when you must wake (or when you will go to bed) and it suggests the times that land on whole-cycle boundaries, then checks your sleep debt against the recommendation for your age.
Why cycle timing helps
Through the night you move through repeating cycles of light, deep and REM sleep lasting around 90 minutes each. Waking at the end of a cycle — in lighter sleep — generally feels far easier than being dragged out of deep sleep mid-cycle, which causes that heavy, groggy "sleep inertia". So rather than picking a round number of hours, the calculator works backwards (or forwards) in 90-minute blocks, adds the time it takes you to fall asleep, and offers several options. Aiming for 5–6 complete cycles — about 7.5 to 9 hours — suits most adults.
Sleep debt and consistency
The tool also estimates sleep debt: the running shortfall between what you need for your age and what you actually get. Small nightly deficits add up quickly, and the best repair is slightly earlier nights on a consistent schedule rather than marathon weekend lie-ins, which themselves disrupt your body clock. Consistency — similar bed and wake times daily — is the single most powerful sleep habit.
Use it as a guide
Ninety minutes is an average; your cycles vary, so treat the suggested times as smart targets, not a guarantee of a perfect morning. Good light habits (dim evenings, bright mornings) and limiting late caffeine matter just as much as timing. This tool gives general information for education, not medical or dietetic advice; consult a qualified professional for guidance about your health. Persistent poor sleep deserves a conversation with a doctor.