Tools · Sleep
Wake Window Calculator by Age
Use this wake window calculator to see how long a baby can typically stay awake at their age, and when the next nap might fit after the last wake-up.
Enter your baby's age to see their typical wake window.
Wake windows vary between babies — watch for tired cues (rubbing eyes, fussiness, staring off) alongside this estimate rather than relying on the clock alone.
These are the starting ranges the Whispie app uses. There is no official standard for wake windows; they vary between babies — watch your baby’s tiredness cues too.
Want this as a running timer? In the Whispie app the next nap time shows in the app and the home-screen widget; it starts from these age-typical wake windows and adjusts to your baby’s own logs (next nap times free for the first 3 active days, then Premium).
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This article is for general information and is not a substitute for professional medical advice. Always consult your pediatrician or doctor about your child.
Sources: WHO, CDC, AAP and NHS guidance. Recommendations differ between countries — for local advice see the NHS or CDC.
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How Wake Windows Change With Age
In the Whispie app’s starting table, the wake window lengthens steadily: 40–110 minutes in the first 2 months, 65–125 minutes at 2–4 months, 90–150 minutes at 4–6 months, 115–185 minutes at 6–9 months, 150–240 minutes (2.5–4 hours) at 9–12 months and 165–250 minutes at 12–18 months. At 18–24 months it is 4–5.5 hours as babies move to one nap; from 24 months the upper value is the last stretch awake between the nap and bedtime (24–30 months: 4.5–7.5 hours; 30–36 months: 5–8 hours).
These are the starting ranges the Whispie app uses. There is no official standard for wake windows; they vary between babies — watch your baby’s tiredness cues too.
These figures are only a starting point. Your own baby's actual window on any given day depends on how their previous sleep went, whether they're teething or unwell, and their individual temperament — a generic calculator can only give you the population-level starting point.
Frequently Asked Questions
What is a wake window?
A wake window is the stretch of time a baby can comfortably stay awake between two sleep periods before becoming overtired. It naturally lengthens as babies get older and their sleep pressure builds more slowly — a newborn's window is measured in minutes, while a 2-year-old's can stretch to several hours.
How long should wake windows be for a 6-month-old?
In the starting table the Whispie app uses, a 3-month-old (2–4 months) has a typical wake window of 65–125 minutes, a 6-month-old (6–9 months) 115–185 minutes and an 11-month-old (9–12 months) 150–240 minutes. Type your baby's age into the calculator above to see the wake windows by age for any month. There is no official standard for wake windows and babies differ, so treat the range as a starting point and watch for tired cues.
How do I work out the next nap time?
Enter your baby's age and the time they last woke up. The calculator adds the lower and the upper end of the typical wake window to that time and shows the result as a range. For example, a 6-month-old who woke at 7:00 gets a range of 8:55 to 10:05. It is an estimate: if your baby shows tired cues earlier, or is content a little longer, follow your baby.
What are the wake windows for a newborn?
In the starting table, babies under 2 months have the shortest wake windows: 40–110 minutes. The range grows with age — 65–125 minutes at 2–4 months and 90–150 minutes at 4–6 months. Newborns vary a lot from day to day, so use the range as a guide. If you have questions about your baby's sleep, talk to your health visitor or pediatrician.
What happens if I miss the wake window?
Going past a baby's wake window tends to trigger an overtired state — paradoxically, an overtired baby often becomes harder, not easier, to settle, and may fight sleep or wake more during the following sleep period. Watching for early tired cues (rubbing eyes, staring off, fussiness) alongside the estimated window helps you catch the right moment.
My baby seems to need a shorter or longer window than the estimate — is that a problem?
No. Wake windows vary meaningfully between individual babies of the same age, and even for the same baby from morning to evening (windows before the first nap are often shorter than windows later in the day). Treat the number as a starting point to watch from, not an exact rule to enforce.
Do wake windows change during sleep regressions or developmental leaps?
Often, yes — temporarily. During a developmental leap or regression, some babies need a slightly shorter window than usual because they're more easily overstimulated, while others briefly resist sleep and need a bit longer. These effects usually settle back to the typical pattern within a couple of weeks.
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