What time should I go to bed? A formula, not a guess

There's no universal bedtime. Work backward from your fixed wake time: subtract your age band's sleep need, then subtract another 15–20 minutes for how long you take to fall asleep. That subtraction — not a number off a chart — answers what time should I go to bed.

What time should I go to bed? Three subtractions

Bedtime = wake time − sleep need − sleep latency.

Every input is something you can name, and two you can measure on yourself. Run it in that order. Reversing it — picking a bedtime you like and hoping the morning cooperates — is why most schedules drift. There's an optional fourth step, rounding to a sleep-cycle boundary, covered below.

Start with wake time, because it's the fixed input

Your wake time is set by a commute, a kid, or a first meeting — not by preference. Pick the earliest one your week actually demands and treat it as constant, weekends included. A wake time that slides two hours on Saturday drags the whole schedule with it, and Sunday night turns into a fight.

Morning light at a consistent hour is also the strongest anchor for circadian timing, a second reason to nail down the wake end first.

Subtract the sleep your age band needs

Sleep need is age-banded, and the bands are wider than most advice admits:

• Teens (14–17): 8–10 hours
• Adults (18–64): 7–9 hours
• Adults 65+: 7–8 hours

Seven hours is a floor for adults, not a target — sleep medicine guidance treats regularly sleeping less than seven as associated with worse health outcomes. Where you land inside the band is individual and fairly stable year to year. If you have no idea, start at 8 hours and let morning alertness move you. How much sleep you need by age covers the bands in detail.

Subtract 15–20 minutes of sleep latency

Sleep latency is the gap between lights out and actual sleep onset. Healthy sleepers usually need somewhere between 10 and 20 minutes. This is the step nearly every "best time to go to bed" chart skips: it tells you when to be asleep, you climb into bed at exactly that time, and the difference comes out of your total.

Budget 20 minutes if you don't know your own number yet. A target sleep onset of 11:00 p.m. means lights out at 10:40 p.m. — and being in the bedroom, teeth done, phone parked somewhere else, before that.

Round to a sleep cycle only when it's free

Cycles average roughly 90 minutes, but the honest range is closer to 70–120, and they vary within a single night: early cycles run shorter and carry more deep sleep, later ones stretch out and tilt toward REM. "Wake at a cycle boundary" is an approximation, not something you can time to the minute. The stages of sleep explains what's moving underneath.

As a tiebreaker it still earns its keep. Inside the adult 7–9 hour band, the cycle-friendly landing spots are 7.5 hours (five cycles) and 9 hours (six cycles). But if your need is genuinely 8 hours, sleep 8 — never cut 30 real minutes to make the arithmetic tidy. Quantity beats cycle geometry.

Worked examples: 6, 7, and 8 a.m. wake times

Assuming an 8-hour need and a 20-minute buffer, with the five-cycle alternative in the last column:

Wake time	Asleep by (8 hrs)	Lights out	7.5-hr option: lights out
6:00 a.m.	10:00 p.m.	9:40 p.m.	10:10 p.m.
7:00 a.m.	11:00 p.m.	10:40 p.m.	11:10 p.m.
8:00 a.m.	12:00 a.m.	11:40 p.m.	12:10 a.m.

Shift a whole row 30 minutes earlier if you need 8.5 hours, or 30 later if 7.5 is truly enough for you.

A computed bedtime only works if something fires at it. Ten forty at night is precisely when you're least likely to remember a calculation you did at nine in the morning, and the target slides a little further every week. Bedtime Reminder is a bedtime reminder app for iPhone, which handles the part arithmetic can't — showing up at the same time every night.

Use your fall-asleep time as feedback

Once the target is running for a week or two, how long you take to drop off tells you whether it's placed correctly.

Under 5 minutes. That's not efficiency, it's sleep pressure. Going out on contact most nights usually means you're carrying debt. The fix is more sleep, not a tighter routine — move lights out earlier and watch whether onset stretches back toward normal.

Roughly 10–20 minutes. Well placed. Leave it alone.

Over 30 minutes, most nights. Two common causes, calling for opposite responses. The first is a target set ahead of your circadian window: you're in bed before your body is ready, and lying there awake teaches the bed to mean "awake." Move lights out 15 minutes later, not earlier. The second is arousal — caffeine too late, a stressful hour before bed, bright screens, a room that's too warm — and that one doesn't respond to bedtime math at all. Onset trouble past 30 minutes on three or more nights a week, running for months, is worth raising with a doctor rather than answering with a stricter bedtime.

Adjust in 15-minute steps

Hold the wake time still. Move lights out by 15 minutes, keep the new time for three or four nights, then check onset and morning alertness before moving again. Bigger jumps outrun circadian timing, so you lie awake, read that as failure, and go back to the old schedule.

If your current schedule is hours off rather than minutes, that's a different job — see how to fix a sleep schedule.

Why "the healthiest bedtime" is the wrong frame

Headlines float numbers like 10 p.m. as though the clock does the work. It doesn't. What matters is total sleep, night-to-night consistency, and alignment with your own circadian timing, and chronotypes vary enough that one person's comfortable onset is another's forced early night.

The average bedtime for adults describes how people live, not what they should do. It's pulled around by work start times, commutes, and age, and it says nothing about the person reading it. Your healthiest bedtime is the one that delivers your band's hours ahead of a wake time you can hold on a Saturday.

FAQ

How long should it take to fall asleep?

Ten to 20 minutes is typical for a healthy adult. Under 5 minutes on most nights points to sleep debt; past 30 minutes on most nights points to a bedtime set too early, to pre-bed arousal, or both. Keep the estimate loose — a rough sense of the number is plenty, and clock-watching makes onset worse.

What time should I wake up if I go to bed at 11 p.m.?

If lights go out at 11:00 p.m., you're probably asleep near 11:20. Eight hours puts your wake time around 7:20 a.m.; seven and a half puts it at 6:50. Run the math the other direction when you can, though — the wake time is the part that should stay fixed.

Is 10 p.m. the best time to go to bed?

Only if you wake around 6 a.m. and need eight hours. Ten o'clock gets repeated as a universal answer, but it's just one row of the same subtraction. What time you should go to sleep depends on your wake time and your band, not on the number itself.

What's the average bedtime for adults?

Late evening, and it shifts with work schedules, age, and country. Averages are useful for noticing that a whole population is under-slept. They're useless as a personal target, because they blend early risers and night owls into a figure that fits neither.

Does going to bed at a different time every night matter?

Yes. Steady timing is easier on circadian regulation than a schedule that swings, and irregular bedtimes tend to shrink total sleep, since the wake time usually stays fixed anyway. A 30-minute spread is fine. A two-hour weekend shift is what makes Monday hard.