Four months is when sleep changes shape. Sleep cycles mature into adult-like stages, so a baby who used to sleep through a transition now surfaces at the end of every cycle. This is what gets called the four-month sleep regression, and it is a permanent developmental change rather than a phase that reverses. The day usually still holds four naps, with the last one short.
Wake at 7:00 AM, 4 naps of about 55 min each, bedtime at 7:30 PM. Nap times are windows, not deadlines — anywhere inside one counts.
| Part of the day | Clock time | Notes |
|---|---|---|
| Wake | 7:00 AM | |
| Nap 1 | 8:30–9:25 AM | 1 h 30 min awake first |
| Nap 2 | 11:10 AM–12:05 PM | 1 h 45 min awake first |
| Nap 3 | 1:45–2:40 PM | 1 h 45 min awake first |
| Nap 4 | 4:40–5:35 PM | 2 h awake first |
| Bedtime | 7:30 PM | 2 h awake first |
The planner adjusts it to your baby's own wake time, bedtime, and birthday — including corrected age if your baby was born early.
The sample day above lands at 3.5 h of daytime sleep and 11.5 h overnight — 15 h in 24. A baby at the bottom of the range who wakes up happy is not short on sleep; the range is wide because babies are.
Over the next month the fourth nap drops and the wake windows lengthen toward two hours. If naps suddenly shorten to 30–45 minutes, the schedule is usually not the cause — the sleep-cycle change is.
Want the wake windows on their own, without the whole day around them? See 4 month old wake windows.
The Tier-1 range is 3.5–5 hours of daytime sleep and 10–12 hours at night, so roughly 13.5–17 hours in 24. Individual babies sit anywhere in that band; a baby at the low end who wakes happy is not short on sleep.
Mostly not. The regression is a change in how sleep cycles are structured. A schedule that is close to the age ranges will not prevent it, though an overtired day makes it harder. Check the wake windows first, then stop adjusting.
About 90 minutes to 2 hours, shortest first thing in the morning and longest before bedtime. The Tier-1 bracket for 3–5 months is 75–150 minutes.
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.