Whispie · Sleep
How Whispie Works Out Your Baby's Next Sleep Time
How the Whispie baby sleep app works out the next nap time from wake windows and your own logs, what it does from birth to 9 weeks, what is free and what is Premium, and what it can't do.
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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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Disclosure: We make Whispie. This page describes the app as of version 4.4 (October 2026). The description of how it works was checked against the app's code by the people who build it.
How is the next sleep time worked out?
1. It starts from your baby's age
Every baby starts with the typical wake window for their age: how long a baby of that age usually stays awake between sleeps. You can see the same ranges in our wake window chart.
2. It adjusts to your own logs
As you log sleep, Whispie looks at how long your baby has actually been awake before recent sleeps, at different times of day. It splits the day into blocks (early morning, morning, midday, afternoon, evening, night) and uses the middle value of your baby's last 10 awake stretches in each block. It needs at least 5 logs in a daytime block, and 2 at night, before it uses your baby's own number there; until then it uses the age-based value for that block.
3. It shows a window, not a minute
The next sleep is shown as a short window, usually 15 to 30 minutes wide, based on how far your baby's sleeps have landed from earlier suggestions over the last 30 days. It is the time we suggest you start trying, not the time your baby will fall asleep.
4. It counts from the last wake-up
The main input is how long your baby has been awake since the last logged sleep, with day and night treated differently. If no wake-up has been logged for 20 hours, the time is marked as an estimate and no reminder is sent.
What is free and what is Premium?
As of October 2026. Premium and Premium+ are subscriptions with a 7-day free trial for new subscribers. Premium+ uses the same timing method as Premium and adds the Sleep Coach (from 6 months).
| Feature | Free | Premium |
|---|---|---|
| Age-based wake windows | Yes | Yes |
| Next sleep and next feed times | Your first 3 active days (accounts created from 8 Oct 2026) | Yes |
| Uses your baby's own awake times | Yes, while times are shown | Yes |
| Nap windows and bedtime from your baby's history (after about 15 logged sleeps), blended with the age range | — | Yes |
| Estimated wake-up time while your baby sleeps | — | Yes |
| Optional reminder before the next sleep, 5 to 30 minutes ahead (iOS) | While times are shown | Yes |
| Lock screen countdown (Live Activity, iOS 16.2+) | While times are shown | Yes |
What can't it do?
- No times before 9 weeks. Under 9 weeks (corrected age, if you entered a preterm birth), Whispie shows "Today so far": the day's totals of feeds, wet diapers and sleep. Newborn sleep is short and spread across day and night; the National Sleep Foundation gives 14 to 17 hours a day for 0 to 3 months.
- It doesn't know when your baby is ill, teething or travelling. It doesn't change for illness, travel or a time-zone change; on those days, follow your baby.
- It only knows what you log. Missed logs make the suggestion less useful.
- It doesn't use the length of the last nap or how many naps there have been today to set the next time directly.
- Corrected age for babies born early is used only if you fill in "Born early?" (before 37 weeks, used up to 24 months). It then applies to wake windows, the 9-week start and reminders. Vaccines and the age shown in the app use the actual birth date.
- It is not medical advice. If you are worried about your baby's sleep, talk to your pediatrician or health visitor.
What happens to your data?
Your logs are stored on Whispie's server and kept on your phone while you are offline. Only the family members you invite can see or add to your baby's logs. Your baby's sleep, feeding and diaper logs are not sent to ad networks or to AI services. Details are in our privacy policy.
Frequently asked questions
Is there an app that tells me when my baby's next nap is?
Yes, several baby sleep apps suggest a next nap time from wake windows. Whispie is one, which we make: it starts from the typical wake window for your baby's age, adjusts it to your baby's own logged awake times, and shows the next sleep as a short window on the home screen (and lock screen on iPhone). Next sleep times are free for your first 3 active days, then part of Whispie Premium.
Does Whispie predict naps for newborns?
No. Whispie shows sleep times from 9 weeks (corrected age if you entered a preterm birth). Before that it shows the day's totals of feeds, wet diapers and sleep instead.
Does the free version use my baby's own logs?
Yes. While next sleep times are shown, the free version also adjusts the age-based wake window to your baby's own logged awake times. Premium adds nap windows and a bedtime built from your baby's longer history, blended with the age range, and an estimated wake-up time while your baby sleeps.
Will my baby fall asleep at the time Whispie shows?
Not necessarily. The time is when we suggest you start trying, shown as a short window. Babies vary from day to day, so watch your baby's tired signs too.
Does Whispie support premature babies?
Yes, if you enter it. Fill in "Born early?" for a baby born before 37 weeks and Whispie uses corrected age (up to 24 months) for wake windows, the 9-week start and reminders.
Where is my baby's data kept?
Your logs are stored on Whispie's server and shared only with the family members you invite. Your baby's sleep, feeding and diaper logs are not sent to ad networks or to AI services.
Sources
- National Sleep Foundation: How many hours of sleep do you really need?
- Paruthi S, et al. Recommended amount of sleep for pediatric populations: AASM consensus statement. J Clin Sleep Med 2016
Comparing apps? See best baby sleep tracking apps and our Huckleberry alternative comparison.
Whispie
Next sleep and feed times that start from age-typical wake windows and adjust to your baby’s own logs, one-tap feeding, sleep and diaper logs, free WHO growth charts, vaccine schedule and week-by-week pregnancy — from expecting to toddler.
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