Bedtime Calculator
Waking up refreshed starts with timing your sleep. Find the best bedtime based on your biological 90-minute sleep cycles.
⚡ Scientific bedtime calculations · Free · No adsI want to wake up at
:
Go to bed at one of these times:
Sleep Cycle Graph Preview
Light Sleep
Deep Sleep (Restorative)
REM Sleep (Dreaming)
How sleep cycles work
Tap any stage to learn what happens in your brain and body
Stage 1 — Light sleep
1–7 min · Easy to wake
You drift between wakefulness and sleep. Eyes move slowly, muscles twitch occasionally. This is when you might feel like you're falling. Your brain produces alpha and theta waves. It's easy to wake someone from this stage — they may not even believe they were asleep.
Stage 2 — Light sleep
10–25 min · Memory consolidation
Eye movements stop. Your heart rate slows and body temperature drops. The brain produces bursts of activity called "sleep spindles" — these are thought to consolidate memories and protect sleep from external noise. You spend about 50% of your total sleep here.
Stage 3 — Deep sleep
20–40 min · Body repairs itself
The hardest stage to wake from. If woken here, you'll feel groggy for 30–60 minutes — this is called "sleep inertia." Your body is hard at work: releasing growth hormone, repairing tissue, building muscle, strengthening bone, and supercharging your immune system. Deep sleep is most abundant in the first half of the night.
REM sleep
10–60 min · Dreaming & creativity
Your brain is as active as when you're awake — this is when vivid dreaming happens. REM stands for Rapid Eye Movement. Your body is temporarily paralysed. REM sleep processes emotions, consolidates creative memories, and is critical for learning new skills. REM periods get longer in the second half of the night — which is why cutting sleep short destroys creativity and emotional regulation.
One full cycle = ~90 minutes. You need 4–6 per night. Waking mid-cycle causes sleep inertia — the heavy, foggy feeling. Waking at cycle end feels refreshing even with fewer hours.