What is corrected age?
A baby born early has had less time to develop in the womb. Corrected age — also called adjusted age — counts a premature baby’s age from the date they were due, rather than the date they were born. It gives a fairer picture when comparing growth and development milestones, such as smiling, sitting or walking, with babies born at full term.
Corrected age = actual (chronological) age − weeks born early
Weeks born early = 40 weeks − weeks of pregnancy at birth
Worked example
A baby born on June 1 at 32 weeks was 8 weeks (56 days) early, so their original due date was July 27. On October 5, the baby’s actual age is 4 months and 4 days, but their corrected age is 2 months and 8 days. When thinking about development, they would be compared with a typical 2-month-old.
How to use the calculator
Enter your baby’s date of birth and the weeks and days of pregnancy at birth (for example 32 weeks and 4 days), which you will find in your discharge or neonatal notes. The calculator shows the actual age, the corrected age, how many weeks early your baby was born and the original due date. If corrected age has not started yet — because the due date has not been reached — it tells you when it will.
When corrected age is used
Corrected age is commonly used for babies born before 37 weeks when assessing growth, development and sometimes feeding — for example when to start solid foods. It is generally used until around age 2, by which time most premature babies have caught up. Vaccinations, however, are usually given by actual age. Always follow the advice of your baby’s neonatal team, doctor or health visitor, who may use corrected age differently for your baby.
For your baby’s actual age in days, weeks and months with milestone dates, use the Baby Age Calculator.