Sleep Calculator
Enter when you want to wake up (or when you're going to bed) and get the times that let you wake at the end of a sleep cycle — so you feel refreshed instead of groggy.
How to use
Pick a mode: 'wake up at' shows the best bedtimes; 'go to bed at' (or 'now') shows the best wake-up times. Each option is a whole number of 90-minute cycles plus ~14 minutes to fall asleep.
Aim for an option that gives you 5–6 cycles (7.5–9 hours). Waking at the end of a cycle — rather than in deep sleep — is what makes mornings easier.
FAQ
How do sleep cycles work?
Sleep runs in ~90-minute cycles through light, deep and REM stages. Waking at the end of a cycle feels natural; waking mid-cycle, especially in deep sleep, leaves you groggy.
Why are 14 minutes added?
That's the average time it takes an adult to fall asleep, so your alarm lines up with the end of a cycle rather than the moment you lie down.
How many cycles do I need?
Most adults do best on 5–6 cycles (7.5–9 hours). Fewer than 4 leaves most people short on sleep.
Is this a substitute for a sleep tracker?
No — it's a timing guide based on average cycle length. Real cycles vary by person and night; use it as a helpful estimate.