Sleep calculator: best bedtime & wake-up time
Choose whether you want to wake up at a set time or go to bed now. The calculator suggests times at the end of full 90-minute sleep cycles.
Voluntary support · Thank-you gift: our checklist PDF · Secure checkout via Digistore24 (Apple Pay, Google Pay, PayPal, card)
🔒 Runs entirely in your browser – nothing you enter is uploaded or stored.
How to use it
- Choose whether you want to wake up or go to bed at a certain time – or go to sleep now.
- Adjust the time you usually need to fall asleep.
- Pick one of the suggested times; 5–6 cycles are ideal for most adults.
Last checked: October 2026. Found a mistake? Use the form below – we fix confirmed errors and update the date.
Frequently asked questions
How long is a sleep cycle?
On average about 90 minutes, with light sleep, deep sleep and REM sleep. Most adults go through 4–6 cycles a night.
Why do I feel tired after a long sleep?
Being woken in the middle of deep sleep causes grogginess (sleep inertia). Waking at the end of a cycle usually feels easier.
How much sleep do adults need?
Health organisations recommend 7–9 hours for adults aged 18–64.