Enter your baby's age and last wake time to find the ideal nap window — the sweet spot between too early (won't sleep) and too late (overtired).
A wake window is the maximum time a baby can comfortably stay awake between sleeps before accumulating too much sleep pressure and becoming overtired. The concept is useful because it's biologically grounded — based on the rate at which adenosine (sleep pressure) accumulates at each developmental stage. Using wake windows rather than clock-based schedules is particularly helpful for young babies whose circadian rhythms aren't yet established.
The overtired trap: When a baby stays awake beyond their wake window, cortisol and adrenaline release as a stress response — making them more alert and harder to settle despite being tired. This is the paradox of the "wired but tired" baby. Starting the nap routine at the first sleep cues (within the wake window) avoids this cycle.