When do babies have growth spurts?
This baby growth spurt calendar turns the ages at which growth spurts are commonly reported — around 2–3 weeks, 6 weeks, 3 months and 6 months — into real dates for your baby, and marks where your baby is today. It also lists the ages when parents often notice sleep changes, sometimes called “sleep regressions”.
Treat every date as a rough window. Babies do grow in bursts, but research shows the bursts come at unpredictable times, so no calendar can tell you when your own baby will have one. Use it to recognise a hungry, fussy few days for what they probably are, not to plan around them.
How to use the growth spurt calculator
- Enter your baby’s date of birth.
- If your baby was born early, choose Count from: due date and enter the due date to use corrected age; ask your health visitor which your clinic uses.
- Read the highlighted window for today and the next one coming up; past windows are greyed out.
- Press Add to calendar to save all the windows, or copy the dates.
Baby Growth Spurt Calendar features
Dates, not just ages
Each typical window shown as a date range from your baby’s birthday or due date.
Today marker
Whether your baby is in a typical window now, and the next one ahead.
Honest labels
Commonly reported ages are separated from those only sometimes mentioned, and sleep “regressions” are marked as a popular term.
Corrected age
Count from the due date for babies born early.
Calendar file
Every window as an all-day event in a standard .ics file.
Typical growth spurt ages
A US state WIC breastfeeding programme puts the first growth spurt at about 2 to 3 weeks and later ones at about 6 weeks, 3 months and 6 months, and notes that they last 1 to 2 days for most babies. Each window on this calendar spans roughly a week or two around those ages.
| Window | How often it is reported | What you may notice |
|---|---|---|
| Around 7–10 days | Sometimes mentioned | Long, frequent feeds as milk supply builds |
| Around 2–3 weeks | Commonly reported | Feeding more often and for longer, cluster feeding in the evening |
| Around 6 weeks | Commonly reported | Hungrier, fussier, shorter sleeps |
| Around 3 months | Commonly reported | More feeds for a day or two |
| Around 4 months | Sometimes mentioned | Feeding and sleep changes together |
| Around 6 months | Commonly reported | Hungrier; around the time solid food starts |
| Around 9 months | Sometimes mentioned | Bigger appetite, busy days |
How strong is the evidence?
Measuring babies very often, researchers found that length grows in short jumps separated by days or weeks with no growth (Lampl and colleagues, Science, 1992) — but the jumps did not fall on fixed ages. The popular ages above come from experience in feeding clinics rather than from studies. Some books and apps sell week-by-week “leap” charts of mental development; their schedule is proprietary and not independently confirmed, so this calendar does not use it.
The same goes for sleep. Changes are often noticed around 4 months, 8–10 months, 18 months and 2 years, alongside new skills, teething and separation anxiety, but “sleep regression” is not a medical term. For a day plan that fits your baby’s age, see the baby sleep schedule.
What helps during a growth spurt
- Feed on cue, even if that is much more often than usual; breast milk supply responds to more frequent feeds within a day or two. The baby feeding chart shows typical amounts for bottle-fed babies.
- Count wet nappies: after the first week, about 6 or more a day is a reassuring sign of enough milk.
- Rest when you can and accept help; it usually passes within a few days.
- A baby who is unwell — fever, poor feeding, unusual sleepiness — is not having a growth spurt. Get medical advice.
Baby Growth Spurt Calendar FAQ
What are the signs of a baby growth spurt?
Feeding more often and for longer, seeming hungry soon after a feed, extra fussiness and changes in sleep, usually for one to a few days.
Is this a baby leap calculator?
No. It does not use any commercial “leap” schedule. It shows the typical growth-spurt ages from breastfeeding guidance, clearly labelled as approximate.
Should I count from the due date or the birth date?
For babies born on time it makes no difference. For premature babies, many professionals use corrected age (from the due date) for development; choose either and compare.
How long does a growth spurt last?
For most babies 1 to 2 days, sometimes up to about a week.
Does my baby need formula during a growth spurt?
Usually not. Feeding on cue builds supply. If you are worried your baby is not getting enough — few wet nappies, poor weight gain — talk to your health visitor or doctor.
Is the growth spurt calendar medical advice?
No. It is general information, as of October 2026, with approximate ages. Seek advice for any illness or feeding worry.