Bedtime Calculator
Bedtime calculator: enter your wake-up time and get the exact time you should go to bed — calculated from 90-minute sleep cycles so you wake at the end of a cycle, not the middle. Free, no sign-up required.
Short answer: the best time to go to bed is 7.5 hours before your alarm, plus your sleep-onset time (~15 minutes for most adults). That puts your alarm at the end of a 90-minute sleep cycle and you wake from light sleep, not deep sleep.
Your ideal bedtimes
Based on a 7:00 AM wake-up
Gold border = recommended. Includes 15-min sleep onset.
Common wake times — ideal bedtime (5 cycles / 7.5 hrs)
Why bedtime timing matters: sleep cycles explained
Sleep is not uniform — it occurs in repeating 90-minute cycles, each containing light sleep, deep (slow-wave) sleep, and REM sleep. If your alarm fires mid-cycle — during deep sleep — your brain is flooded with adenosine (sleep pressure) and melatonin, causing sleep inertia: the groggy, disoriented state that can persist for 30–90 minutes. Waking at the end of a cycle means you surface naturally from light sleep and feel alert almost immediately.
The 15-minute sleep onset adjustment accounts for the fact that you are not asleep the moment you get into bed. The average healthy adult takes 10–20 minutes to fall asleep. If you fall asleep much faster (under 5 minutes consistently), it may indicate significant sleep debt. If it regularly takes over 30 minutes, that is worth noting — see our CBT-I guide for difficulty falling asleep.
Five cycles (7.5 hours of actual sleep) is the optimal amount for most Canadian adults. Six cycles (9 hours) suits recovery periods, illness, and heavy training loads. Four cycles (6 hours) is a workable single-night minimum but causes compounding impairment if sustained — research from the University of Pennsylvania found that after 10 days of 6-hour nights, subjects performed as poorly as those kept awake for 24 hours straight.
Sleep cycles & REM — quick reference
This page doubles as a sleep cycle timer / REM cycle calculator. Each 90-minute cycle progresses through four sleep stages:
- N1 (light sleep) — ~5 minutes; the doze on the edge of sleep
- N2 (medium sleep) — ~20–25 minutes; the bulk of total sleep over the night
- N3 (deep slow-wave sleep) — ~20–30 minutes; physical restoration; dominates the first 2 cycles of the night
- REM (rapid eye movement) — ~10–20 minutes early in the night, growing to 40–60 minutes by the last cycle; consolidates memory and emotional processing
REM share grows in later cycles — which is why cutting sleep short (4 cycles instead of 5–6) disproportionately reduces total REM. If you regularly struggle to fall asleep within 30 minutes, see our CBT-I guide; for the regulatory framework on melatonin and sleep medication in Canada, see the Canadian insomnia guidelines.
Bedtime calculator — frequently asked questions
What time should I go to bed?
The best bedtime is 7.5 hours before your wake-up time (5 complete 90-minute sleep cycles) plus however long it takes you to fall asleep. For a 7 AM wake-up with a 15-minute sleep onset: go to bed at 11:15 PM for 5 cycles (7.5 hrs) or 9:45 PM for 6 cycles (9 hrs). Use the calculator above to get your exact times.
What is the best time to go to bed?
The best time to go to bed is exactly 7.5 hours before you need to wake up, plus your sleep-onset time (typically 15 minutes). That puts your alarm at the end of a 90-minute sleep cycle so you wake from light sleep, not deep sleep. For most adults this means going to bed between 10:00 PM and 11:30 PM if you wake between 5:30 AM and 7:00 AM.
What time should I go to sleep to wake up feeling rested?
To wake up feeling rested, go to bed so that your alarm falls at the end of a 90-minute sleep cycle. Five cycles (7.5 hours of actual sleep) is optimal for most adults. Add 15 minutes for sleep onset. So if you wake at 6:30 AM, go to bed at 11:00 PM (5 cycles) or 9:30 PM (6 cycles).
Should I go to bed now?
If you need to wake up in 7.5 hours from now, yes — go to bed now to get 5 complete sleep cycles. If you have 6 hours or less, you will sleep through fewer than 4 cycles; in that case some sleep researchers recommend going to bed immediately and accepting a 4-cycle (6-hour) night rather than skipping further cycles. The calculator above shows the exact cycle counts for any wake-up time you choose.
How does a bedtime calculator work?
A bedtime calculator counts backward from your wake-up time in 90-minute increments — one for each sleep cycle — then adds your average sleep onset time (how long it takes to fall asleep). The result is the time you should get into bed so your alarm coincides with the natural end of a sleep cycle, when waking feels easiest.
What is a sleep cycle?
A sleep cycle is the ~90-minute progression through the stages of sleep: a few minutes of light sleep (N1), 20–25 minutes of medium sleep (N2), 20–30 minutes of deep slow-wave sleep (N3), then a final 10–20 minutes of REM (rapid eye movement) sleep. Each cycle repeats through the night. Adults need 5–6 full cycles for restorative sleep.
How long is a sleep cycle?
An average adult sleep cycle is 90 minutes (range: 80–110 minutes). Earlier cycles in the night are shorter and contain more deep sleep; later cycles are longer and contain more REM sleep. Bedtime calculators use 90 minutes as the standard cycle length because it is the population average.
Is it better to wake up at the end of a sleep cycle?
Yes — waking at the end of a 90-minute sleep cycle, when you are in light sleep or briefly awake between cycles, produces less sleep inertia than waking from deep sleep mid-cycle. Sleep inertia (the groggy 30–90 minutes after waking) is significantly worse when an alarm fires during N3 deep sleep. Cycle-aligned wake times feel more alert immediately.
Is 6 hours of sleep enough?
Six hours covers 4 complete sleep cycles, which is below the recommended minimum for adults. Research shows that sustained 6-hour nights cause measurable cognitive impairment equivalent to 24 hours of total sleep deprivation after 10 days — even when subjective sleepiness levels off. Seven to nine hours (5–6 cycles) is the range recommended by the Canadian Sleep Society and most international sleep bodies.
What time should I go to bed if I wake up at 6 AM?
If you wake up at 6:00 AM: go to bed at 10:15 PM for 6 cycles (9 hours sleep + 15 min onset), 11:45 PM for 5 cycles (7.5 hours), 1:15 AM for 4 cycles (6 hours), or 2:45 AM for 3 cycles (4.5 hours — minimum). The 11:45 PM bedtime is optimal for most adults.
What time should I go to bed if I wake up at 7 AM?
For a 7:00 AM wake-up: go to bed at 11:15 PM for 5 cycles (7.5 hrs) or 9:45 PM for 6 cycles (9 hrs). These include a 15-minute sleep onset. The 5-cycle option is optimal for most adults; choose 6 cycles when recovering from illness, training hard, or rebuilding from sleep debt.
What time should I go to bed if I wake up at 8 AM?
For an 8:00 AM wake-up: go to bed at 12:15 AM for 5 cycles (7.5 hrs) or 10:45 PM for 6 cycles (9 hrs). Both include a 15-minute sleep onset. The 6-cycle option (10:45 PM) is what most sleep researchers consider optimal for adolescents and young adults, whose circadian rhythm naturally runs later.
Does this bedtime calculator work for shift workers in Canada?
Yes — the calculator works for any wake-up time, including the unusual hours of shift workers. Enter your actual wake time (e.g., 2:00 PM for a night-shift worker), and it returns the optimal bedtime backwards through 90-minute cycles. Canadian shift workers (oil sands, healthcare, trucking, mining) often need to flip schedules across rotations; pairing this tool with strategic light exposure and melatonin is more effective than either alone.
Also need to find the best alarm time?
The full sleep calculator runs in both directions — enter a bedtime and find your optimal wake time, or calculate from right now.
Full Sleep Calculator →