Baby Growth Spurt Calculator (Growth Spurt Dates by Age)
See when your baby's growth spurts are likely: dates for the 7–10 day, 2–3 week, 4–6 week, 3, 6 and 9 month growth spurts from the birth date, adjusted for prematurity, plus the next one coming up and what to expect.
How it works
growth spurt window = birth date (or due date for premature babies) + typical age range · common windows: 7–10 days, 2–3 weeks, 4–6 weeks, 3 months, 6 months and 9 months
Babies don't grow at a steady rate: many go through short bursts of faster growth, when they suddenly want to feed much more often (cluster feeding), are fussier and sleep differently for a few days. The ages most often reported are around 7–10 days, 2–3 weeks, 4–6 weeks, 3 months, 6 months and 9 months, but every baby is different and the timing is approximate. For babies born early, the dates follow corrected age (counted from the due date). Feeding on demand during a spurt is usually all that is needed; breast milk supply follows the extra demand within a few days.
Worked example
For a full-term baby born on September 1, 2026, the windows are: 7–10 days (Sep 8 – Sep 11, 2026), 2–3 weeks (Sep 15 – Sep 22), 4–6 weeks (Sep 29 – Oct 13), 3 months (Nov 24 – Dec 8), 6 months (Feb 16 – Mar 2, 2027) and 9 months (May 25 – Jun 8, 2027). Looking ahead from October 4, 2026, the 4–6 week spurt is happening now. If the same baby had been born 4 weeks early, every window would move 4 weeks later.
Sources: HealthyChildren.org (AAP): Is your baby hungry or full? · Cleveland Clinic: Baby growth spurts
Frequently asked questions
When are baby growth spurts?
Commonly around 7–10 days, 2–3 weeks, 4–6 weeks, 3 months, 6 months and 9 months. These are averages; your baby may have them a little earlier or later, or you may not notice some at all.
How long do growth spurts last?
Usually 2–3 days, occasionally up to a week. Feeding more often for a few days is normal and helps build breast milk supply.
Do premature babies have growth spurts at different times?
They tend to follow their corrected age — counted from the due date rather than the birth date — so enter how many weeks early your baby was born.
When should I worry during a growth spurt?
Call your pediatrician if your baby has fewer wet diapers than usual, signs of dehydration, a fever, is hard to wake, or the fussiness lasts more than a week. A growth spurt should not cause illness symptoms.
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Educational information only, not medical advice or a diagnosis. Discuss your results and any decision with your doctor, midwife or pharmacist.