How do you calculate adjusted age?

Work out how many weeks early the baby was born (40 minus the gestational age at birth), then subtract that many weeks from the chronological age. Equivalently, calculate the age from the due date instead of the birth date.

Until what age is adjusted age used?

Adjusted age is commonly used for developmental assessment up to about 24 months of chronological age. Individual test manuals and clinical guidelines set their own limits, so follow the rule for the test you are using.

Adjusted Age Calculator

Q: What is adjusted age?

Adjusted age, also called corrected age, is a premature child's chronological age minus the number of weeks the child was born before the expected due date (40 weeks of gestation). It estimates how old the child would be if born at term.

For babies and toddlers born early. Enter the date of birth, the test date and how many weeks premature the child was, and get the chronological age and the adjusted (corrected) age together, both in Y;M;D format.

What is adjusted age?

A baby born at 40 weeks of gestation is "term". A baby born earlier has spent less time developing, so on their first birthday they have had fewer weeks to grow than a term baby of the same chronological age. Adjusted age, also called corrected age, compensates for that difference by subtracting the number of weeks the child was born early. A child born at 32 weeks is 8 weeks early; at a chronological age of 12 months, the adjusted age is about 10 months.

Developmental screens and some norm-referenced tests for infants and toddlers instruct examiners to use adjusted age so that a premature child is compared with children at the same developmental stage rather than the same birthday. Pediatric growth charts and milestone checklists often do the same.

How the calculator works

It first calculates the chronological age from the date of birth to the test date, exactly as on the main calculator.
It then moves the birth date forward by the number of weeks (and days) the child was born early. That shifted date is an estimate of the original due date.
The adjusted age is the age counted from that due date to the test date. If the test date is before the due date, the adjusted age is zero.

If you know the actual due date rather than the gestational age, the number of weeks early is simply the number of weeks between the birth date and the due date.

When to stop correcting

The common clinical convention is to use adjusted age for developmental purposes until the child reaches about 24 months of chronological age, after which the difference is considered small enough to ignore. Some guidelines use 36 months for very premature children, and some tests do not correct at all. The calculator flags results at 24 months or older so you can check the rule that applies to your test.

Frequently asked questions

Do I enter weeks early or gestational age?

Enter weeks early: 40 minus the gestational age at birth. A baby born at 34 weeks and 3 days is 5 weeks and 4 days early, so enter 5 weeks and 4 extra days.

Which age goes on the protocol?

Record the chronological age on every form, and additionally record the adjusted age wherever the test manual asks for it. Both are shown here so you can copy each one.

Does this apply to babies born at 37 to 39 weeks?

Babies born at 37 weeks or later are usually treated as term and not corrected, but some guidelines do correct late-preterm infants for the first few months. Follow the guidance of the test or clinic you are working with.