What is corrected age?

It is your baby's age worked out from their due date instead of their birth date, which accounts for how early they arrived. It is used to judge development fairly in premature babies.

Why does it matter for twins?

Twins are often born early, so their birthday age can overstate where they are developmentally. Corrected age gives a fairer picture in the first couple of years.

When do you stop correcting for age?

Most guidance uses corrected age for about the first two years, after which the gap becomes small. Your paediatric team will advise for your baby.

Corrected age calculator for premature babies

Corrected age calculator

Date of birth

Original due date

Worked out in your browser. Nothing you enter is sent anywhere.

Why corrected age matters

A baby born two months early is, developmentally, about two months behind their birthday age at first. Corrected age adjusts for that, so you are comparing like with like when you look at milestones such as smiling, rolling and sitting.

How it is used

Health teams typically use corrected age for roughly the first two years. It is not about your baby being behind; it is about measuring their progress fairly. Your paediatric team will tell you when to switch to actual age.

Quick answer

Corrected age (also called adjusted age) is your baby's age counted from their due date rather than their birth date. For babies born early, including many twins, it is the fairer way to judge development in the first two years. Enter the birth date and the original due date and this tool works out both actual and corrected age in your browser.

How to use it

Enter the birth date. Set the day your baby was actually born.
Enter the original due date. Set the estimated due date from the pregnancy.
Read both ages. You get actual age and corrected age. Milestones in the first two years are often judged on corrected age.

Frequently asked questions

What is corrected age?: It is your baby's age worked out from their due date instead of their birth date, which accounts for how early they arrived. It is used to judge development fairly in premature babies.
Why does it matter for twins?: Twins are often born early, so their birthday age can overstate where they are developmentally. Corrected age gives a fairer picture in the first couple of years.
When do you stop correcting for age?: Most guidance uses corrected age for about the first two years, after which the gap becomes small. Your paediatric team will advise for your baby.