MindgladSleep Calculator
Find the best time to go to bed — or wake up — based on your body’s 90-minute sleep cycles, so you wake up refreshed instead of groggy. No sign-up, completely free.
To wake up feeling refreshed, fall asleep at one of these times:
Based on 90-minute sleep cycles, plus ~15 minutes to fall asleep. Waking at the end of a cycle — not mid-cycle — is what leaves you feeling rested.
Why timing your sleep in cycles matters
You don’t sleep at one steady depth all night. You drift through repeating cycles — light sleep, deep sleep, then REM — each lasting roughly 90 minutes. Waking at the end of a cycle, when sleep is naturally lightest, feels easy and clear. An alarm that goes off in the middle of deep sleep is what makes you feel like you’ve been hit by a truck, even after a full night.
This calculator does the maths for you. Tell it when you need to wake up and it counts backward in 90-minute cycles (plus about 15 minutes to actually fall asleep) to show you the best bedtimes. Or tell it when you’re heading to bed, and it shows the best times to set your alarm.
How much sleep do you really need?
Most adults feel best on 5–6 complete cycles — that’s 7.5 to 9 hours — which is why those options are marked as recommended above. Consistency matters as much as length: going to bed and waking at similar times trains your body clock, so falling asleep gets easier over time.
When the clock isn’t the real problem
Perfect timing only helps if you can actually fall asleep. If you lie awake with a mind that won’t switch off — replaying the day, planning tomorrow, bracing for the 3am wake-up — the issue isn’t your schedule, it’s an over-activated nervous system. That’s exactly what a short guided wind-down is built for: it slows your breathing, loosens tension, and gives a racing mind something calmer to follow.
Sleep calculator FAQ
How does the sleep calculator work?
Sleep happens in cycles of about 90 minutes. You move from light sleep into deep sleep and REM, then back toward light sleep. Waking up at the end of a cycle — when sleep is lightest — leaves you feeling refreshed, while waking mid-cycle leaves you groggy. This calculator counts back (or forward) in 90-minute cycles from your chosen time and adds about 15 minutes to fall asleep, so you can target the end of a cycle.
How many hours of sleep do I actually need?
Most adults do best on 7–9 hours, which is 5 to 6 full sleep cycles. That’s why the 7.5-hour and 9-hour options are marked as recommended. If you can only get 6 hours, aiming for a clean 4 cycles still beats waking up partway through a fifth.
What time should I go to bed to wake up at 6am?
To wake at 6:00 AM rested, aim to fall asleep around 8:46 PM (6 cycles / 9 hours) or 10:16 PM (5 cycles / 7.5 hours). Add the ~15 minutes most people take to drift off, and head to bed a little before those times. Switch the calculator to “wake up at” and enter 6:00 AM to see your exact times.
Why do I wake up tired even after 8 hours?
Two common reasons: you woke in the middle of a deep-sleep cycle, or your sleep was fragmented by a racing mind, stress, or late screens — so those 8 hours weren’t fully restorative. The calculator fixes the timing; a short guided wind-down helps with the quality.
Is REM sleep the same as a sleep cycle?
No — REM is one stage within each ~90-minute cycle, along with light and deep sleep. REM gets longer toward morning. Because REM sits near the end of a cycle, waking at a cycle boundary usually means waking just after REM, which feels natural.
This tool is for general wellbeing and education only. It is not medical advice. If you have ongoing insomnia or a sleep disorder, please speak with a qualified healthcare professional.