What time should I go to bed?

Your ideal bedtime depends on three things: your required wake time, your age, and the number of sleep cycles you want to complete. Formula: Bedtime = wake time − (cycles × 90 minutes) − 14 minutes The 14 minutes accounts for the average time it takes to fall asleep (sleep onset latency). Examples with 7:00 AM wake time: - 5 cycles (7.5h): bedtime 11:16 PM — good minimum for most adults - 6 cycles (9h): bedtime 9:46 PM — ideal for recovery or high activity Age-specific answers: - School-age children (6-13): 8:00-9:30 PM for a 7 AM wake - Teenagers (14-17): 9:00-10:30 PM for a 7 AM wake - Adults (18-64): 9:30-11:30 PM for a 7 AM wake Consistency matters more than the exact time: Once you choose a bedtime, stick to it within 30 minutes every night — including weekends. Your circadian rhythm (internal clock) runs on a ~24.2 hour cycle and is reset daily by consistent sleep and wake times combined with light exposure. Varying your bedtime by more than an hour between days disrupts this rhythm and reduces sleep quality even when total hours are maintained.

What is social jetlag and why is it harmful?

Social jetlag is the difference between your biological sleep timing and your socially required sleep timing — in practice, it is the gap between when you sleep on weekdays versus weekends. Definition (Wittmann et al. 2006): Social jetlag = |weekday wake time − weekend wake time| Example: - Weekday wake: 6:30 AM (forced by work/school) - Weekend wake: 9:00 AM (natural preference) - Social jetlag: 2.5 hours Why it happens: Most people have a natural sleep timing (chronotype) that is later than their social obligations require. Night owls forced to wake early on weekdays try to 'catch up' by sleeping in on weekends — but this shifts the biological clock later, making Monday morning even harder. Health effects of chronic social jetlag (>1-2 hours): - Increased obesity risk: disrupts leptin/ghrelin (hunger hormones) - Higher rates of depression and anxiety - Greater cardiovascular risk - Impaired glucose metabolism (type 2 diabetes risk) - Reduced cognitive performance throughout the week - Increased likelihood of mood disorders The solution is NOT to give up weekend sleep — it is to gradually shift your weekday bedtime later (if your schedule allows) so the gap narrows. Alternatively, keep weekday and weekend wake times within 1 hour of each other even if bedtime varies. You cannot 'pay back' sleep debt: Research shows catching up on weekends partially compensates for weekday sleep loss, but does not restore full cognitive performance or metabolic health. Consistent sleep timing is the only sustainable solution.

Why do children need so much more sleep than adults?

Children need more sleep than adults for several interconnected biological reasons: 1. Brain development: - The brain grows most rapidly in the first 5 years of life - Sleep — particularly N3 deep sleep — is when the brain consolidates new neural connections - Children form thousands of new synapses daily; sleep prunes and strengthens them - The prefrontal cortex (decision-making, impulse control) continues developing until age 25 2. Growth hormone release: - ~70% of human growth hormone (HGH) is released during N3 deep sleep - Children in growth spurts require more deep sleep for this hormonal work - Chronic sleep deprivation in children can impair physical growth 3. Memory and learning consolidation: - Children learn enormous amounts of language, social rules, motor skills daily - Sleep consolidates these learnings from short-term to long-term memory - A study by Kurdziel et al. (2013) found napping after learning improved test scores by 10% 4. Immune function: - Children's immune systems are actively building (encountering new pathogens) - Sleep is when immune memory (antibodies) is consolidated - Sleep-deprived children are significantly more susceptible to illness Practical bedtimes for school-age children (7 AM wake): - Age 6: 7:00-8:00 PM (10-11 hours needed) - Age 8: 7:30-8:30 PM (10 hours) - Age 10: 8:00-9:00 PM (9-10 hours) - Age 12: 8:30-9:00 PM (9 hours) - Age 13: 9:00 PM (8.5-9 hours)

Does everyone really need 8 hours of sleep?

No — sleep need is biologically determined and varies between individuals. '8 hours' is a rounded population average, not a universal prescription. The real distribution: - About 35% of adults genuinely need 7 hours or less - About 50% need 7.5-9 hours - About 15% need more than 9 hours (long sleepers) - Fewer than 3% are true genetic short sleepers (DEC2 gene) who function on 6 hours How to find YOUR sleep need: 1. On a week with no obligations, go to bed when tired and wake without an alarm 2. After 3-4 days of catching up on debt, note how long you sleep naturally 3. This is your biological sleep need Signs your current sleep amount is insufficient: - You need an alarm to wake up (a natural sleep need means natural waking) - You feel sleepy within 2 hours of waking - You can fall asleep in less than 5 minutes in the afternoon - Weekends you naturally sleep 2+ hours longer than weekdays - Caffeine feels necessary (not just enjoyable) to function Age-related changes in sleep need: - Sleep need is relatively stable from young adulthood through age 60 - Sleep architecture changes with age (less N3, more nighttime awakenings) - Older adults often sleep earlier and lighter — not because they need less, but because circadian rhythms advance with age The 'I'm fine on 6 hours' myth: Studies show people chronically sleeping under 7 hours dramatically underestimate their impairment. After 2 weeks of 6h sleep, subjects performed like the 24h sleepless group — but rated themselves as 'only slightly sleepy'.

What is the best routine before bed to fall asleep faster?

A consistent pre-sleep routine (sleep hygiene) significantly improves both how quickly you fall asleep and your sleep quality: 2-3 hours before bed: - No vigorous exercise (raises core temperature; needs 2-3h to drop to sleep-optimal levels) - Limit alcohol (disrupts REM and causes fragmented second-half sleep) - Start dimming lights gradually — bright light suppresses melatonin 1-2 hours before bed: - Dim all screens or switch to night mode — blue light (460nm) suppresses melatonin by up to 50% - Avoid work-related mental activity — activates problem-solving brain regions - Light activity: reading (physical book), gentle stretching, meditation - Ideal bedroom temperature: 16-19°C (61-67°F) — body temperature must drop 1-2°C to initiate sleep 30-60 minutes before bed: - No screens at all (phones, tablets, TV) - Write a 'to-do list' for tomorrow — externalising worries reduces intrusive thoughts - Consider journaling or noting 3 things you are grateful for (reduces cortisol) - Consistent pre-sleep cue: the same activity every night (tea, reading, gentle music) conditions the brain to associate that activity with sleepiness If you cannot fall asleep after 20 minutes: - Get out of bed — lying awake in bed trains your brain to associate bed with wakefulness - Do something calm in dim light (reading, gentle stretching) - Return to bed only when sleepy - This is stimulus control — a key component of CBT-I (most effective insomnia treatment)

Bedtime Calculator — By Age Group & Wake Time

The Bedtime Calculator finds the ideal bedtime for any age group based on a required wake time and number of 90-minute sleep cycles, with 14 minutes added for sleep onset latency. Eight age groups from newborn to older adult with NSF-recommended sleep hours. Optional weekend wake time input calculates social jetlag (we..

FIND YOUR BEDTIME

AGE GROUP

WEEKDAY WAKE-UP TIME

SLEEP CYCLES (7-9h recommended for Adult (18-64 yr))

YOUR IDEAL BEDTIME

11:16

WAKE TIME

7:00 AM

SLEEP

7h 30m

CYCLES

Set alarm for 7:00 AM · Go to bed by 11:16 PM

WEEKLY SLEEP SCHEDULE

Mon

11:16 PM → 7:00 AM

7h 30m

Tue

11:16 PM → 7:00 AM

7h 30m

Wed

11:16 PM → 7:00 AM

7h 30m

Thu

11:16 PM → 7:00 AM

7h 30m

Fri

11:16 PM → 7:00 AM

7h 30m

Sat

11:16 PM → 7:00 AM

7h 30m

Sun

11:16 PM → 7:00 AM

7h 30m

🔵 Blue bar = sleep window · Weekend shown with light blue background

NSF SLEEP NEEDS BY AGE

Age Group	Hours	Bedtime if wake 7am
👶 Newborn (0-3 mo)	14–17h	2:16 PM – 5:16 PM
🍼 Infant (4-11 mo)	12–15h	3:46 PM – 6:46 PM
🧸 Toddler (1-2 yr)	11–14h	5:16 PM – 8:16 PM
🎨 Preschool (3-5 yr)	10–13h	5:16 PM – 8:16 PM
📚 School age (6-13 yr)	9–11h	8:16 PM – 9:46 PM
🎒 Teenager (14-17 yr)	8–10h	8:16 PM – 11:16 PM
🧑 Adult (18-64 yr)	7–9h	9:46 PM – 11:16 PM
👴 Older adult (65+ yr)	7–8h	11:16 PM – 11:16 PM

CONSISTENCY IS THE KEY

The most important factor is not what time you go to bed — it is that you go to bed and wake up at the same time every day. A consistent wake time anchors your circadian rhythm better than any other intervention.

Created with ❤️ byeaglecalculator.com

HOW TO USE

1
Select your age group from 8 options covering every life stage from newborn to older adult. Selecting an age group automatically sets the recommended number of sleep cycles to the midpoint of that age group's NSF-recommended range and highlights which cycle counts are age-appropriate in the list below.
2
Enter your weekday wake-up time using the hour and minute inputs with AM/PM toggle. Quick-select buttons cover the most common school and work wake times from 5 AM to 9 AM. The bedtime options update live as you type — you can see all your options before settling on a final time.
3
Optionally enable 'Different weekend wake time' to enter a separate wake time for Saturday and Sunday. The calculator will compute your social jetlag — the difference between weekday and weekend wake times — and flag it as green (manageable) if under 1.5 hours or red (health risk) if over 1.5 hours.
4
Choose the number of sleep cycles from the list. Each row shows the cycle count, total sleep duration, and the resulting bedtime in large numerals. Options within your age group's recommended range are highlighted green with a tick. Click any row to select it — the hero result card and weekly schedule update instantly.
5
Check the right panel for your weekly sleep schedule — all 7 days shown as rows with a blue bar indicating the sleep window, plus the exact bedtime-to-wake-time for each day. Weekdays and weekends are visually distinguished. The NSF reference table shows all age groups with their recommended hours and example bedtimes for a 7 AM wake.

WORKED EXAMPLE

Bedtime Calculator — worked examples: FORMULA: Bedtime = wake time − (cycles × 90 min) − 14 min EXAMPLE 1: Adult, wake 7:00 AM (= 420 min from midnight) 5 cycles (7.5h): 420 − (5×90) − 14 = 420 − 450 − 14 = −44 min −44 mod 1440 = 1396 min → 23h 16min → 11:16 PM ✓ 6 cycles (9h): 420 − (6×90) − 14 = 420 − 540 − 14 = −134 min −134 mod 1440 = 1306 min → 21h 46min → 9:46 PM ✓ Verify: 11:16 PM + 14 min onset + 5×90 min = 11:16 + 0:14 + 7:30 = 7:00 AM ✓ EXAMPLE 2: School child (age 10), wake 7:00 AM, needs 9-10h (6-7 cycles) 6 cycles (9h): 420 − 540 − 14 = 9:46 PM bedtime ✓ 7 cycles (10.5h): 420 − 630 − 14 = 8:16 PM bedtime Recommended bedtime for age 10, wake 7 AM: 8:16 PM – 9:46 PM EXAMPLE 3: Social jetlag Weekday wake: 6:30 AM | Weekend wake: 9:00 AM Social jetlag = |6:30 AM − 9:00 AM| = 2.5 hours ⚠ Over 1.5h — associated with increased metabolic risk AGE-BASED REFERENCE (wake 7:00 AM): School (6-13): 8:16 PM – 9:46 PM (9-11h) Teen (14-17): 8:16 PM – 11:16 PM (8-10h) Adult (18-64): 9:46 PM – 11:16 PM (7-9h)

REFERENCE FORMULAS

FORMULA REFERENCE TABLE

Concept	Formula	Description
Bedtime	Bedtime = wake time − (cycles × 90 min) − 14 min	Works back from required wake time. 14 min = average sleep onset latency (time to fall asleep).
Sleep cycle	1 cycle = 90 minutes (N1→N2→N3→REM)	One complete progression through all 4 sleep stages. Duration ranges 80-120 min; 90 min is the average.
Adult recommendation	7–9 hours = 5–6 cycles	NSF recommendation for adults 18-64. 5 cycles (7.5h) is a good minimum; 6 cycles (9h) is ideal.
Child recommendation	9–11 hours for ages 6-13	Younger children need more sleep: toddlers 11-14h, preschool 10-13h. Growth hormone released in N3.
Social jetlag	\|weekday wake - weekend wake\|	Difference in wake times between weekdays and weekends. >1.5h associated with metabolic disruption.
Circadian rhythm	Anchored by consistent wake time ± 30 min	The body clock runs on a 24.2h cycle, reset daily by light. Consistent wake time is the most powerful reset.

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Last updated: April 29, 2026 · Sleep recommendations: National Sleep Foundation · Social jetlag: Wittmann et al. (2006) · 90-min cycle average: Carskadon & Dement