Bedtime Calculator
Updated for 2026 · All math runs privately in your browser
Tell us when you need to wake up. We'll count backwards in 90-minute sleep cycles so your alarm lands between cycles — when waking up feels easy — and draw your whole night as a hypnogram.
Your schedule
Set the time your alarm actually has to go off.
Most people drift off in 10–20 minutes. Be honest — it shifts every bedtime.
Your ideal bedtimes
Hypnogram of your night
- Wake-up time—
- Time to fall asleep—
- Sleep cycles—
- Total sleep—
Estimates based on the average 90-minute sleep cycle. Real cycles vary between 80–120 minutes and shift through the night.
How to use this calculator
- Enter the time you must wake up — when the alarm rings, not when you'd like to get up.
- Adjust minutes to fall asleep to match how long you usually lie awake.
- Pick a bedtime from the options. 5 cycles (7.5h) is the sweet spot for most adults; 6 cycles is even better.
- Read the hypnogram: each block is one 90-minute cycle of light → deep → REM sleep.
How the math works
Bedtime = wake-up time − (cycles × 90 minutes) − minutes to fall asleep. For a 7:00 AM alarm, 5 cycles and 15 minutes to drift off: 7:00 AM − 7h 30m − 15m = 11:15 PM.
Why cycles matter: each ~90-minute cycle runs light sleep → deep sleep → REM (dreaming). Waking at a cycle boundary means you surface from light sleep, which is why some mornings feel effortless and others feel like wading through mud.
The hypnogram above draws your night the way sleep labs do: every cycle is split into its three phases so you can see exactly when deep sleep and dreaming happen.
Frequently asked questions
It counts backwards from your wake-up time in 90-minute sleep cycles, then subtracts the minutes you need to fall asleep. Waking up at the end of a cycle — during light sleep — feels far better than being yanked out of deep sleep mid-cycle.
A full sleep cycle — light sleep, deep sleep, then REM — lasts about 90 minutes in most adults. Sleep researchers use the 90-minute cycle as the standard unit because waking between cycles avoids sleep inertia, that heavy groggy feeling.
For most adults 18–64, the National Sleep Foundation recommends 7–9 hours, so 5 full cycles (7.5 hours) sits squarely in the healthy range. Six cycles (9 hours) is ideal if your schedule allows it.
You wake during deep sleep or REM, which triggers sleep inertia — grogginess, disorientation and low energy that can last 30 minutes or more. That's why the calculator aims your alarm at the end of a cycle.
Most healthy adults fall asleep within 10–20 minutes of lying down (sleep latency). The calculator defaults to 15 minutes; adjust it if you know you drift off faster or slower.
Backwards from a fixed wake time works best, because most people must wake at a set hour. If your bedtime is the fixed part of your schedule instead, pick a wake time that lands on a cycle boundary after it.