What Is Corrected Age (Adjusted Age)?

Corrected age, also called adjusted age, is a premature baby’s age counted from the original due date instead of the birth date. It shows how old the baby would be if they had been born at full term, 40 weeks. This corrected age calculator, also known as an adjusted age calculator or premature baby age calculator, does the math for you to the exact day.

Doctors, nurses and therapists use corrected age to judge growth and milestones fairly. A baby born 10 weeks early has had 10 fewer weeks to develop in the womb, so comparing them with full-term babies of the same chronological age would be misleading.

How to Use This Corrected Age Calculator

1. Enter the date of birth of your premature baby.
2. Set the “age on” date. It starts on today; change it to the day of a check-up or assessment.
3. Tell us how early the baby was born. Enter the gestational age at birth in weeks and days (for example 30 weeks 2 days), or switch to the original due date.
4. Press Calculate Corrected Age. You get the corrected age and chronological age side by side, the number of weeks born early, the due date, and a note on whether correction still applies.

Not sure of the gestational age? It is usually on the hospital discharge papers. Doctors estimate it from the last menstrual period or an early ultrasound, and a gestational age calculator can work it out from the due date and the actual delivery date. Leave “age on” set to the current date to see the age today.

This preemie age calculator works for any preterm baby born between 22 and 42 weeks. If the baby was born at 37 weeks or later, it tells you no correction is needed.

How to Calculate Corrected Age

1. Work out how early the baby was born. Subtract the gestational age at birth from 40 weeks. Born at 32 weeks = 8 weeks early.
2. Find the chronological age. Count from the birth date to today, or use our chronological age calculator.
3. Subtract the weeks born early. The answer is the corrected age.

Born at	Weeks early	Chronological age	Corrected age
36 weeks	4	3 months	about 2 months
32 weeks	8	6 months	about 4 months
28 weeks	12	9 months	about 6 months
26 weeks	14	12 months	about 9 months

Our corrected age calculator does this to the exact day by adding the weeks born early to the birth date, then counting years, months and days to the test date.

Corrected Age Example With Real Dates

Ayesha was born on 2 March 2026 at 31 weeks and 3 days. On her check-up on 15 September 2026:

• Weeks born early: 40w 0d − 31w 3d = 8 weeks 4 days (60 days)
• Due date: 2 March 2026 + 60 days = 1 May 2026
• Chronological age: 6 months, 13 days
• Corrected age: 1 May to 15 September = 4 months, 14 days

So her doctor compares her growth and skills with a typical 4½-month-old, not a 6-month-old. Enter the same dates in the corrected age calculator above to check the result.

Premature Birth Categories

How much correction a baby needs depends on how early they arrived. The World Health Organization groups preterm births like this:

Category	Gestational age at birth	Weeks early
Extremely preterm	Less than 28 weeks	More than 12
Very preterm	28 to under 32 weeks	8 to 12
Moderate to late preterm	32 to under 37 weeks	3 to 8
Term	37 weeks or more	No correction needed

Why Adjusted Age Matters for Premature Babies

Using adjusted age for premature babies gives parents and doctors a fair picture of progress. A baby born 3 months early may not sit, babble or roll at the same chronological age as a full-term baby, and that is usually expected. Measured by corrected age, the same baby is often right on track.

Corrected age is typically used for growth charts, feeding and solid food timing, and for motor, language and cognitive milestones such as smiling, sitting, crawling and first words. It helps avoid unnecessary worry, and it helps professionals notice a real delay early.

Common Mistakes When Calculating Corrected Age

• Subtracting months instead of weeks. Babies are born early by weeks and days; converting to rough months adds errors. A good adjusted age calculator works in days.
• Forgetting the extra days. 29 weeks 6 days is almost 30 weeks, not 29.
• Correcting for too long. After about 2 years, most care teams switch back to chronological age.
• Correcting full-term babies. Babies born at 37 weeks or later do not need a corrected age.

Corrected Age vs Chronological Age

	Chronological age	Corrected age
Counted from	Birth date	Due date
Used for	Birthdays, school, legal forms	Growth, milestones, development checks
Applies to	Everyone	Babies born before 37 weeks
Usually used until	Always	About 2 years old

When Do You Stop Using Corrected Age?

Most doctors use corrected age until around 2 years (24 months) of chronological age. By then, most premature babies have caught up, and the few weeks’ difference matters less. Some specialists continue a little longer for babies born very early, so follow the advice of your child’s care team.

Corrected Age for Developmental Testing

Many developmental and speech-language assessments ask for corrected age when a child was born prematurely and is under a certain age. Check the test manual, record both ages on the protocol, and see our test age ranges and chronological age for testing guides.

To compare skills with milestones, try the developmental age calculator or read chronological vs developmental age.

Corrected Age Calculator FAQs

What is corrected age for premature babies?

Corrected age, also called adjusted age, is a premature baby’s age counted from the due date instead of the birth date. It tells you how old the baby would be if born at 40 weeks.

Example: a baby born 8 weeks early who is 6 months old has a corrected age of about 4 months.

How do you calculate adjusted age for a premature baby?

Subtract the number of weeks the baby was born early from the baby’s chronological age. Weeks early = 40 weeks − gestational age at birth.

Example: a 5-month-old born at 34 weeks was 6 weeks early, so the adjusted age is about 3½ months. The calculator above works this out to the exact day.

What is corrected gestational age?

Corrected gestational age, also called postmenstrual age, is used before the baby reaches the due date, often in the NICU. It equals the gestational age at birth plus the time since birth.

Example: a baby born at 28 weeks who is now 6 weeks old has a corrected gestational age of 34 weeks. Once the baby passes 40 weeks, corrected age in months is used instead.

Until what age should corrected age be used?

The American Academy of Pediatrics recommends correcting for prematurity until about 2 years of age. By then most premature children have caught up.

For babies born very early, some specialists and developmental tests continue correcting a little longer. Follow your child’s care team and the test manual.

Does a baby born at 37 weeks need a corrected age?

No. Babies born at 37 weeks or later are full term, so their chronological age is used. The calculator shows “no correction needed” for these babies.

Should vaccines be given by corrected age?

No. The CDC recommends giving most vaccines to premature babies by chronological age, the same schedule as full-term babies. Ask your child’s doctor about any exceptions.

Should growth charts use corrected age?

Yes. Doctors usually plot a premature baby’s weight, length and head size by corrected age, typically until about 2 years. Before the due date, special preterm growth charts are used in the NICU.

When should a premature baby start solid foods?

Most guidance bases this on corrected age, often around 6 months corrected, together with readiness signs such as good head control and sitting with support. Check with your baby’s doctor first.