An interval is the awake time from waking until the next sleep starts. It is different from nap length. You do not need to guess a number to use this page.
Leave with a useful record, even without a time estimate
Record the last wake time you know. Mark other times as unknown if needed.
Record whether a nap happened, was tried without sleep, or was not offered. Keep these different.
Save what you have for yourself or another caregiver. Add the next actual sleep when it happens.
A missed nap by itself cannot choose a new bedtime. Keep following any existing care instructions; use the guide to review your situation rather than inventing an interval.
We add your interval to the last recorded wake time. With ranges, the earliest wake plus the shortest interval gives the earliest result; the latest wake plus the longest interval gives the latest result. Later planned naps use your assumed duration, so uncertainty can widen.
Trying to settle without sleep and not offering a nap do not reset the wake time. Unknown times remain unknown. A plan never becomes a recorded event just because its time has passed.
These calculations do not determine when a baby will sleep, recommend a nap transition, or diagnose a sleep problem. No age-based rules are approved in this version. Follow any professional care plan and seek professional advice for health concerns or persistent difficulties.
Method and sources
Current method: user-defined interval arithmetic, version 1. No medical review is claimed. For general sleep and care information, see American Academy of Pediatrics: baby sleep. That resource is not used to derive an individual wake interval.
Compare tonight using the information you have
Start with the last known wake time and your own interval. A short, late, or missed nap does not automatically trigger a minute adjustment. You can compare two sets of assumptions and check a preferred evening range.
You do not need a complete sleep history. Keep unknown times unknown. A plan is only selected when you choose it, and it never adds sleep to the recorded total.