An infant is generally considered a child from birth up to 1 year old.

Typical medical/parenting definitions

  • Many health and government sources define infant as a child younger than 1 year of age.
  • The period right after birth (up to about 1–3 months) is often called the newborn stage, but the baby is still also an infant.
  • After about 1 year, the child is usually called a toddler , especially from 1 to about 3 years.

Why definitions vary a bit

  • Some medical classifications mark “neonate” (newborn) as birth to 28 days, then “infant” from 28 days up to 1 year.
  • Parenting and childcare articles often describe “newborn” as birth to about 2–3 months, then “infant” up to 12 months.

So when people ask “how old is an infant,” the most accepted answer is: from birth until the child turns 1 year old. Information gathered from public forums or data available on the internet and portrayed here.