How old is your baby really?
Babies born early are measured from their due date, not their birthday. Enter both and we’ll do the maths.
Fill in the dates to see your baby’s corrected age.
This is a friendly estimate, not medical advice. Corrected age is a guide for milestones and growth, and every premature baby catches up on their own timeline — always go by what your pediatrician tells you.
About corrected age
What is corrected age?
Corrected age (also called adjusted age) is your baby’s age counted from their original due date instead of their birthday. A baby born eight weeks early has a corrected age eight weeks behind their actual age. It’s the fairer yardstick for a premature baby, because it measures how long they’ve been developing rather than how long they’ve been out in the world.
How do you calculate corrected age?
Take your baby’s age today and subtract how early they arrived. If your baby is 5 months old and was born 2 months before their due date, their corrected age is 3 months. If you know the gestational age at birth instead, the weeks early are simply 40 minus the weeks your baby was born at — a baby born at 32 weeks was 8 weeks early.
Until what age do you correct?
Most doctors correct until around 2 years, by which point the gap has usually closed and actual age works fine. For babies born very early — before about 28 weeks — some clinicians keep correcting until age 3. Your pediatrician will tell you when to stop for your baby.
Should I use corrected age for milestones and vaccines?
It depends on what you’re measuring. Milestones and growth charts follow corrected age — expect your baby to roll, sit, and smile on their corrected schedule, not the calendar one. Vaccines follow actual age: shots are scheduled from the birthday and are not delayed for prematurity. Starting solids usually goes by corrected age plus signs of readiness, so ask your pediatrician.
What counts as premature?
A baby born before 37 weeks of pregnancy is premature. Within that, birth at 34–36 weeks is late preterm, 32–33 weeks is moderately preterm, 28–31 weeks is very preterm, and before 28 weeks is extremely preterm. The earlier the birth, the longer corrected age tends to stay useful.
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