Who this is for: For the daily 5 PM question — "what time is bedtime tonight?" — after naps went long, short, or vanished entirely, especially during the 2→1 nap transition.
Enter your baby's age and the time the last nap ended — get the bedtime window that fits the age's final wake window.
Quick answer: Bedtime = last nap end + the final wake window for the age: about 60–90 minutes at 3 months, 2.5–3.5 hours at 9 months, 4–5 hours at 18 months. On broken-nap days, an earlier bedtime beats stretching a tired baby.
The time your baby actually woke from the final nap.
Suggested bedtime
7:00 PM
last nap end + 3 h 30 min final window
Bedtime window
6:30 PM–7:15 PM
±15 min cushion built in
Final wake window
3 h–3 h 30 min
9–10 months · longest of the day
On broken-nap days, earlier beats later: a bedtime 30–60 minutes before this suggestion is the standard fix for an overtired evening — it does not cause early waking. If this bedtime lands past 8:30 PM, tomorrow consider capping the final nap earlier. General guidance for 9–10 months — not medical advice.
Core facts
Output
Bedtime window (+/− 15 min cushion)
Inputs
Age + last nap end time
Rule
Bedtime = last nap end + final wake window
Compiled
September 2026
How does the bedtime calculator decide?
Bedtime falls at the end of the last wake window: the age's longest stretch of awake time, measured from when the last nap ended. The calculator adds that window to your input and returns a suggested bedtime plus a ±15-minute cushion. Two adjustments matter in real life: if the last nap ran short or ended early, an earlier bedtime protects the night (a 30–60 minute early bedtime is the standard fix for an overtired evening); if the nap ran very long into the late afternoon, the window may push bedtime later than you'd like — cap that nap and keep bedtime near the age-typical range.
Common uses
Setting bedtime after a late or extra-long afternoon nap
Pulling bedtime earlier on days when naps fell apart
Checking whether a 7 PM bedtime even matches your baby's age
Planning the evening routine backwards from the bedtime window
Where these ranges come from
Ranges are compiled in September 2026 from widely used pediatric sleep resources (Huckleberry sample schedules, Taking Cara Babies, Full Feedings and similar). Sources disagree by ±15 min at the edges — treat the range, not one number, as the target and watch your baby's sleep cues.
Frequently Asked Questions
Should bedtime be fixed or nap-dependent?
Both have a case. A fixed clock bedtime builds strong routine cues; nap-dependent bedtime (last nap end + final wake window) adapts to real days. Many families use a fixed target with ±45 minutes of drift based on the last nap.
Is an early bedtime bad?
No — an earlier bedtime is the standard tool against overtiredness. A baby who napped poorly often sleeps better going down 30–60 minutes early, and it does not cause early waking as commonly as feared.
What if bedtime lands later than 8–9 PM?
Check the last nap: if it ended at 4:30 PM or later, the window pushes bedtime late. Capping the final nap (wake by mid-afternoon for most ages over 6 months) keeps bedtime in the age-typical 7–8:30 PM zone.
Does the final wake window differ from the others?
It's usually the longest of the day — sleep pressure has all day to build. The calculator uses the top of your baby's age range for it, which is why bedtime lands later than the last nap-to-nap gaps.
Is this a medical recommendation?
No — general guidance compiled September 2026 from widely used pediatric sleep resources. For persistent night waking or suspected sleep disorders, talk to your pediatrician.