Most bedtime advice starts with a number. The useful version starts with your wake time and works backwards, because the wake time is the part that is fixed.
Work backwards, not forwards
1. Fix your wake time. Set by work, school, or the earliest commitment you have most days. This is the anchor — it is the one your alarm enforces and the one that entrains your clock. (Why the wake time is the anchor.)
2. Subtract the sleep you need. Seven to nine hours for most adults. Individual need is fairly stable and mostly genetic; if you consistently wake unprompted feeling fine after 7.5 hours, that is your number.
3. Add 20 to 30 minutes for sleep onset. Falling asleep is not instant. Healthy sleep onset is roughly 10 to 20 minutes, and building in a margin means you are not doing arithmetic that assumes you fall asleep the moment you lie down.
For a 6:30am wake and eight hours: asleep by 10:30pm, so in bed around 10pm.
That is the whole calculation. Everything else is about whether you can actually sleep at that time.
The constraint most people miss
You cannot just pick a bedtime. Two things have to be true.
Sleep pressure has to be high enough. Adenosine accumulates the longer you are awake. Go to bed three hours early and it simply has not built up.
You have to be inside your circadian sleep window. Melatonin release is timed by your clock, which is set by light. If your clock says 1am and you are in bed at 10pm, you will lie there.
This is why "just go to bed earlier" fails so often, and why lying awake for an hour is worse than useless — it teaches your brain that bed is a place where you are awake.
Moving your bedtime earlier, properly
If your target is meaningfully earlier than your current bedtime, shift it rather than jumping.
Move in 15-minute steps every few nights. Faster than that and you are just lying awake.
Anchor the wake time first. Get up at your target time immediately, even while the bedtime is still drifting in. This builds sleep pressure and pulls the clock forward from the other end. It costs you a few rough days.
Get outside first thing. Morning light advances the clock and is the strongest tool available. (How much and for how long.)
Keep evenings genuinely dark. Late bright light delays the clock, which is precisely the direction you are fighting. (The dimming protocol.)
Cool the room and consider a warm bath 90 minutes before, both of which steepen the core temperature fall that sleep onset runs on. (Why the bath works.)
Your chronotype sets the range
Some of this is not negotiable. Chronotype is substantially genetic, and a genuine night owl forced onto a 10pm bedtime is fighting biology, not laziness.
Light timing can shift your window by an hour or two. It will not turn a late chronotype into an early one.
If your job allows any flexibility, aligning work to your chronotype does more than any bedtime discipline. If it does not, the realistic goal is to minimise the mismatch rather than eliminate it — and to stop treating it as a character flaw. (What the weekend catch-up costs.)
Consistency beats the specific time
Worth stating plainly: a consistent 11:30pm beats an inconsistent 10pm.
Regularity of sleep timing predicts health outcomes at least as well as duration in several studies. A stable schedule your clock can entrain to is more valuable than an earlier one you keep abandoning.
Which also means weekends count. A three-hour weekend shift is a transatlantic-scale timing change twice a month.
When the bedtime is not the problem
If you go to bed at a sensible hour, sleep the right number of hours, and still wake exhausted, the timing is not your issue. Something is fragmenting the night.
Common and fixable: alcohol, a hot room, and disrupted breathing. (Work the checklist.) (What one drink costs you.)
Mouth breathing fragments sleep through micro-arousals you never remember, which is why hours can look adequate on paper and deliver nothing. Titan's mouth tape is a full strip rather than vented, since a vent lets you keep mouth breathing without noticing — provided your nose is clear. (What a full night of nasal breathing changes.)
And if you snore heavily, gasp awake, or feel exhausted regardless of hours, get assessed before adjusting anything. (How to decide.)
The bottom line
Fix the wake time, subtract your sleep need, add half an hour for onset. That is your bedtime.
Then check it is achievable: enough sleep pressure, and inside your circadian window. Shift in 15-minute steps, anchor the wake time first, and get light early. A consistent later bedtime beats an inconsistent earlier one every time.