Babies gain weight fastest in the first months, then the pace gradually slows over the first year.

Typical weight gain speed (big picture)

  • Most full‑term babies lose up to about 7–10% of their birth weight in the first few days, then usually regain it by around 2 weeks of age.
  • Many babies double their birth weight by about 4 months and triple it by around 12–15 months (a bit earlier for boys on average).

Week‑by‑week / month‑by‑month pace

The numbers below are averages, not targets; a healthy baby can be above or below them and still be doing well.

  • 0–2 weeks
    • Normal to lose some weight, then start gaining again by day 5 or so.
* Goal is mainly “back to birth weight” by about 10–14 days.
  • 5 days to 4 months
    • About 5–7 ounces per week (roughly 170 grams per week), which comes out to around 1 ounce (28 g) per day in the early weeks.
* This is the “rapid growth” phase; many babies look noticeably chubbier month to month.
  • 4 to 6 months
    • About 4–6 ounces per week (113–150 grams per week), so growth is still steady but not quite as fast as in the newborn phase.
* Around this time, daily gain often drops from about 28 g to nearer 20 g per day or less.
  • 6 to 12 months
    • About 2–4 ounces per week (57–113 grams per week); some days you may not see much change, but the trend over weeks still goes up.
* By 12 months, many babies are roughly triple their birth weight.

Breastfed vs formula‑fed babies

  • Breastfed newborns often gain a bit faster than formula‑fed babies in the first 3 months.
  • After about 3 months, formula‑fed babies are more likely to gain a bit faster on average.
  • Both patterns can be completely healthy; doctors use standard WHO growth charts for both feeding types up to age 2.

What’s “normal” vs “concerning”?

Normal variations:

  • Short “slow” weeks after vaccines, illness, or big developmental leaps.
  • Some babies follow a lower curve steadily but keep the same general percentile over time.

Reasons to call your pediatrician or other local child‑health provider:

  • Your baby has not regained birth weight by about 2 weeks.
  • Weight gain suddenly flattens or drops off their usual growth curve.
  • Very sleepy baby who is hard to wake for feeds, very few wet diapers, or signs of dehydration (very dry mouth, fewer tears, sunken soft spot).

An example: if a 2‑month‑old is gaining roughly 5 ounces a week, waking for feeds, making plenty of wet diapers, and is alert between feeds, most clinicians would consider that very reassuring, even if the baby is smaller or larger than friends’ babies the same age.

TL;DR: In the first months, many babies gain around 1 ounce (28 g) per day, slowing to roughly 2–4 ounces per week by the second half of the first year, with birth weight usually doubled by 4 months and tripled by around 1 year.

Information gathered from public forums or data available on the internet and portrayed here.