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Free tool

Baby wake windows calculator

Tell us your baby’s age and when they last woke up. We’ll tell you the exact range when their next nap should start.

From the night or from their last nap

How to read the result

The range we give you is the optimal window to start sleep: begin the nap wind-down 10–15 minutes before the range opens, and try not to let it slip past. Before the range, your baby will lack sleep pressure; after it, overtiredness starts working against you.

For the theory, read the full guide to wake windows by age, and find your stage’s details in baby sleep by age.

The automatic version: Siestita

This calculator uses age averages. The Siestita app does the same with your baby’s data: it logs every nap and waking, learns their real rhythm and alerts you to the next window without you typing anything. It’s the difference between a good estimate and their actual schedule.

FAQ

Calculator FAQs

How does it calculate the next nap?

It adds the recommended wake window for your baby’s age (for example, 2.5–3.5 hours at 8 months) to the time of their last wake-up. The result is the range where falling asleep will be easiest.

How accurate is the range?

It’s an estimate based on age averages — an excellent starting point. The exact version for your baby comes from their real data: the Siestita app learns from every logged nap and tunes the prediction to their specific rhythm.

Does it work for bedtime too?

Yes: if the wake-up you enter is from the last nap of the day, the range we give you is their ideal bedtime. The last window of the day is usually the longest in the range.

What if the previous nap was very short?

Subtract 15–20 minutes from the range: after a nap under 45 minutes, babies usually need sleep earlier than scheduled.

Automatic calculation, every day

With the Siestita app, the next nap will work itself out from your baby’s real sleep — no manual input needed.

Coming soon to the App Store and Google Play