Most wake-window advice gives you one number per age and leaves it there. In practice the windows across a day are not equal, and the one that decides how the night goes is the last one.
What a wake window is
A wake window is the stretch a baby can comfortably stay awake between sleeps. Too short and they have not built enough sleep pressure to fall asleep or stay asleep; too long and they tip into being overtired, which makes settling harder, not easier.
What is well established is the total. The AASM consensus is 12–16 hours per 24 hours for infants aged 4–12 months, including naps, and 11–14 hours for one- to two-year-olds.[1]
Why the last window should be the longest
Sleep pressure builds the whole time a baby is awake and is discharged by sleeping. Each nap discharges some of it. That means the pressure available at bedtime depends almost entirely on how long your baby has been awake since the last nap ended.
A short final window sends a baby to bed with too little pressure. They fall asleep on tiredness alone, then surface at the end of the first cycle with nothing left to carry them into the next one — which is where a long, cheerful wake-up in the middle of the night comes from.
| Age | First window | Middle windows | Last window before bed |
|---|---|---|---|
| 0–3 months | 45–60 min | 45–75 min | 60–90 min |
| 3–6 months | 1h 15m–1h 45m | 1h 30m–2h | 2h–2h 30m |
| 6–9 months | 2h–2h 30m | 2h 30m–3h | 3h–3h 30m |
| 9–12 months | 2h 30m–3h | 3h–3h 30m | 3h 30m–4h |
| 12–18 months | 3h–4h | 4h–5h | 4h–5h 30m |
The pattern matters more than the numbers: shortest first thing in the morning, longest before bed. A baby who has just slept a long night needs the least time to rebuild pressure; by evening they need the most. How long each window actually runs varies a lot between babies and keeps changing as they grow, which is why any published range is a starting point rather than a target.[2][3]
How to stack the windows
Work backwards from bedtime rather than forwards from the morning.
- 1
Fix bedtime first
Pick the bedtime you actually want and treat it as the anchor. Everything else is arranged to arrive there with enough sleep pressure.
- 2
Set the last nap to end at the right distance
Count the longest window for your baby's age back from bedtime. That is when the last nap needs to end — which usually means capping it rather than letting it run.
- 3
Keep the first window short
After a full night, sleep pressure is at its lowest. A short first window gets the day started without fighting for a nap that will not come.
- 4
Let the middle windows absorb the slack
If a nap runs short, add the difference to a middle window rather than to the last one. The final stretch is the one to protect.
- 5
Give it four or five days
A schedule change takes several days to show. Judging it after one night tells you about that night, not about the schedule.
Signs the last window is too short
- Bedtime takes a long time despite obvious tiredness.
- A long, content wake-up in the middle of the night — not distressed, just awake.
- Early morning waking that does not respond to an earlier bedtime.
Signs it is too long
- Frantic, difficult settling; crying that escalates rather than winding down.
- Falling asleep instantly in the car or pram late in the day.
- Short first stretch of night sleep followed by frequent waking.
Overtiredness and undertiredness both produce a bad night, which is why bedtime resistance alone does not tell you which way to move. Change one thing, hold it for several days, and watch the middle of the night rather than bedtime itself.
Work it out for your baby
Our free wake window calculator takes an age and a wake time and returns the day's windows, naps and bedtime — a starting point to adjust from, not a schedule to enforce.
