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Plan your sleep around your body clock

Restcalc calculates the perfect bedtime or wake-up time using natural 90-minute sleep cycles, so you rise during light sleep — refreshed, not groggy.

Bedtime Calculator

Enter the time you need to wake up. We count back in 90-minute sleep cycles plus ~15 minutes to fall asleep.

Times assume ~15 min to fall asleep. Earlier bedtimes give you more complete cycles.

Wake-up Calculator

Enter when you plan to go to bed. We add sleep cycles to find the best moments to wake up.

Waking at the end of a cycle means ending in light sleep — easier to get up.

Sleep Duration Checker

Enter your bedtime and wake time to see total sleep, completed cycles, and a quality rating.

Nap Calculator

Enter the current time to see the best window for a refreshing power nap or a full-cycle nap.

Keep naps before 3 PM and under 90 minutes to protect nighttime sleep.

Sleep Window Helper

Choose the time range you are free to sleep. We find the best bedtimes that complete full 90-minute cycles and wake you inside your window.

Assumes ~15 min to fall asleep. Best windows wake you at the end of your range; sleep earlier if you prefer.

Sleep Log & Trend

Log a few nights — just your bedtime, wake time, and how you felt. We turn it into a visual trend using the 90-minute cycle model.

DateBedtimeWakeFelt
Tip: fill from the most recent night back. Entries stay on this device only — nothing is uploaded.

Your sleep over time

Caffeine Cutoff Calculator

Enter your planned bedtime and sensitivity. We work back to your last safe cup.

A guideline, not medical advice. Caffeine half-life varies between people.

Pre-Sleep Meal Calculator

Enter your planned bedtime and what you are eating. We work back to the latest time you should finish.

A guideline, not medical advice. Digestion speed varies between people.
Read the full guide: why late eating hurts sleep →

Bedtime Breathing Timer

Choose a rhythm, press start, and breathe with the circle. Inhale as it grows, exhale as it shrinks.

Ready
04:00

Slow breathing is a relaxation aid. If breath-holding makes you light-headed, anxious, or uncomfortable, stop.

How sleep cycles work

A good night is not just about hours — it is about timing.

Your brain moves through sleep cycles about every 90 minutes, alternating between light sleep, deep sleep, and REM (dream) sleep. A full night usually holds 4–6 cycles. Waking up between cycles — during light sleep — leaves you clear-headed; waking mid-deep-sleep is what causes grogginess. Restcalc simply works backwards from your alarm (or forwards from bedtime) to land you on a cycle boundary.

Science-backed sleep tips

Small habits, big difference.

Frequently asked questions

Everything you need to use Restcalc confidently.

Sleep products we recommend

Gear that helps you fall — and stay — asleep.

Restcalc is a participant in the Amazon Associates program. As an affiliate we may earn from qualifying purchases, at no extra cost to you. Links are marked “sponsored”.

About Restcalc