What time to sleep to wake at 7am
Bedtimes for 4, 5 and 6 cycles, so you hit full night's rest.
90-minute sleep cycles
Wake at the end of a cycle
Your body sleeps in ~90-minute cycles. Wake mid-cycle and you'll feel foggy no matter how long you slept. Plan your timer backwards — and wake up ready.
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Why full sleep cycles matter
Sleep repeats in cycles of roughly 90 minutes. Each cycle moves through light sleep, deep sleep (where the body repairs) and REM (where you dream and process memory). Waking is easiest in the light-sleep phase right at the end of a cycle.
If your alarm fires mid-deep-sleep, you experience sleep inertia — grogginess that lingers for 30 minutes or more. The times below land your alarm at the natural end of a cycle, so you surface on your own terms.
Power-nap helper
How long should the nap be?
min
min
The two sweet spots
20 minutes, or a full 90
Short naps of 20 minutes let you recharge before deep sleep sets in. If you have time for a full 90-minute cycle you'll get deep and REM sleep — but land the alarm at the cycle end, or the sleep inertia returns.
- Pick a plan — wake-up or bedtime-first.
- Enter a time and watch cycles map backwards.
- Count the cycles — 5–6 is the sweet spot.
- Nap short — 20 min, or commit to 90.
Sleep cycle questions
How long is one sleep cycle?
Most people cycle in about 90 minutes. A full night is generally 4 to 6 cycles — roughly 6 to 9 hours of sleep depending on the person and age.
What happens if I wake mid-cycle?
You wake from deep or REM sleep, which triggers sleep inertia — grogginess, impaired focus and a slow brain for up to half an hour or more after you get up.
Is the 20-minute nap effective?
Yes. A 20-minute nap ends before deep sleep begins, so it boosts alertness and mood without causing grogginess on waking. It's the sweet spot for a quick recharge.
Should I count how long I take to fall asleep?
Yes — that's why the calculator adds a fall-asleep buffer. Average sleep latency is about 10–20 minutes, and adding it makes your bedtime estimate much more accurate.