Turn these windows into clock times
A four-month-old typically manages 90 minutes to two hours awake, shortest first thing in the morning and longest before bed. This is the age where windows start to feel like they work — and also the age where sleep cycles mature, so a window that was right last month may need stretching this month.
| Wake window | Length | Where it falls |
|---|---|---|
| Window 1 | 1 h 30 min | after morning wake-up |
| Window 2 | 1 h 45 min | between naps |
| Window 3 | 1 h 45 min | between naps |
| Window 4 | 2 h | between naps |
| Window 5 | 2 h | before bedtime |
The same day with clock times, naps and bedtime is on the 4 month old sleep schedule page.
If naps collapse to 30–45 minutes at four months, the wake window is usually not the culprit: that is one sleep cycle, and surfacing between cycles is what changes at this age. Try one adjustment, give it several days, and stop there.
About 90 minutes to 2 hours. The Tier-1 bracket for 3–5 months is 75–150 minutes, and most four-month-olds sit in the middle of it.
Usually, yes — the first window of the day is the shortest and the one before bed the longest. That is a practice-based convention rather than a rule; some babies do the opposite.
Use corrected age, not birth age. A baby born eight weeks early has the wake windows of a two-month-old at four months old. The planner does this adjustment for you.
Tier 1 — evidence-based The ranges on this page are the consensus sleep totals and nap counts below. The phrase "wake window" itself is a Tier 2 practice-based heuristic: it does not appear in the pediatric sleep-medicine literature, so treat the window lengths as a starting estimate and let your baby's sleepy cues override them.