Bedtime Calculator

How the bedtime calculator works

A bedtime calculator takes the time you need to wake up and works backward through natural 90-minute sleep cycles. We add about 15 minutes to fall asleep, then subtract full cycles (4, 5 or 6) to show the bedtimes that land you on a cycle boundary. Wake at the end of a cycle and you surface during light sleep — the easiest point to get up.

If you have ever wondered "what time should I go to bed to wake up at 7am", the answer is rarely a round number. It depends on how many complete cycles fit before your alarm. The calculator shows a few options so you can pick the one that matches your evening.

Why time your bedtime by sleep cycles?

Sleep is not one continuous block. Your brain moves through roughly 90-minute cycles of light, deep and REM sleep, usually 4–6 per night. Waking mid-deep-sleep is what causes morning grogginess; waking between cycles feels natural. Planning bedtime around these boundaries is the core idea behind every tool on Restcalc, and it is grounded in sleep science such as the National Sleep Foundation's duration guidance (2022).

A few quick tips

• Earlier bedtimes give you more complete cycles before a fixed wake time.
• Keep a consistent wake time — it stabilizes your whole cycle.
• Aim to wake at a 90-minute boundary using the times above.