Baby Sleep Window
Every nap battle is a timing battle. Put in your baby's age, get the minutes they can stay happy awake, before the cortisol spike makes sleep impossible.
Window shape (AASM / Sleep Foundation consensus): newborn 45–60 min → 3 mo 75–95 → 6 mo 105–135 → 9 mo 135–165 → 12 mo 150–180 → 18 mo 180–210 → 2 yr 210–300 (one nap) → 3–4 yr 300+ (naps fading). The window is the time from wake to the start of the sleepy-signals, not to collapse, collapse is the window already overshooting.
How the math works
- Wake window: piecewise-interpolated between anchor ages (newborn 45–60, 3 mo 75–95, 6 mo 105–135, 9 mo 135–165, 12 mo 150–180, 18 mo 180–210, 24 mo 210–300). You get a band: start settling at the low end, cap at the high.
- Total sleep targets (AASM pediatric guidance): 0–3 mo 14–17 h, 4–12 mo 12–16, 1–2 yr 11–14, 3–5 yr 10–13. Night share ramps from ~60% (newborn) to ~75% by 6 mo.
- The countdown row runs from the last wake time you enter: the window opens at the low-end mark, closes at the high-end. The green band is where settling works; the red is where you're fighting cortisol.
- 6-month reality: total sleep under 11 h at 4–12 mo is the number to raise with the pediatrician, not to "train away."
What is a wake window for a 6 month old?
2 to 2.25 hours. A 6-month-old on three naps settles best at ~120–135 minutes after each wake; past 150 you're into overtired territory where the nap gets shorter, not longer.
How many hours should a baby sleep at 9 months?
12–16 hours per 24, roughly 10–11 at night plus two naps of 60–90 minutes. The tool splits your target into night share and nap share automatically.
Why does my baby fight the last nap?
The last window is the most over-run (bedtime math). If the last nap ends less than 3.5 h before bedtime, it's too late to work, move bedtime earlier by 15–30 minutes, which is the same sleep debt paid at the cheaper price.