The calculator starts from the wake-up time you want and counts backward using the amount of overnight sleep children typically need at each age. A 9-month-old, for example, needs around 11 to 12 hours of night sleep, so a 7:00 AM wake-up points to a bedtime between 7:00 and 8:00 PM.

The numbers behind it follow widely used pediatric sleep guidelines. They describe what most children need, not a rule your child must match exactly.

Sleep needs vary from child to child, even at the same age. The range shows the healthy zone, and the ideal bedtime in the middle is a strong starting point. How your child wakes up tells you where to land: waking up happy around the desired time means the bedtime fits, while early waking or difficulty getting up in the morning are signs to shift bedtime within the range.

Children can't switch from playing to sleeping on command. The wind-down time is when to start the bedtime routine, dimming lights, bath, pajamas, a book, so your child arrives at bedtime calm and ready rather than mid-play. Starting the routine on time is often the difference between a smooth bedtime and a battle.

Yes. The calculator assumes your child had age-appropriate naps today. On a day with short or skipped naps, your child builds up extra tiredness, and moving bedtime 20 to 30 minutes earlier helps prevent an overtired bedtime. After an unusually long or late nap, your child may need a little more awake time before being ready to sleep.

Bedtime battles usually come from timing being off in one of two directions. An overtired child (bedtime too late, or naps too short) gets a burst of stress hormones and fights sleep while clearly exhausted. An undertired child (bedtime too early, or a long late nap) is simply not ready yet. The pattern of your evenings, plus how the night and morning go, points to which one is happening.

A consistent bedtime, within about 30 minutes, helps set your child's internal clock, which makes falling asleep easier and mornings more predictable. Perfect consistency isn't required, and the occasional late night won't undo anything. The rhythm across the week matters more than any single evening.

Babies under 3 to 4 months don't have a set bedtime yet, and this is completely normal. Their sleep runs on short wake windows rather than the clock, and "bedtime" often lands late in the evening at first. An earlier, more predictable bedtime develops naturally around 3 to 4 months.

A calculator can give you a starting point, but it can't see your child. If bedtime is a struggle, nights are broken, or you're unsure what your little one needs, I'd love to help. Hit reply to the email where you received this link and tell me what's going on. Helping families sleep is what I do.