Quick answer
Label every age you write down. Chronological age counts from the birth date; adjusted age accounts for weeks born before term, and only one of them is the legal age.
The same word for two things
"Adjusted age" and "corrected age" are generally used interchangeably for the same calculation: chronological age minus the prematurity interval. Some services prefer one term, some the other, and a few use "postmenstrual age" for a related but distinct measure counted from the last menstrual period.
Because the vocabulary is not settled, the practical rule is to label the number rather than trusting the term. "5 months (corrected)" and "7 months (chronological)" are unambiguous to any reader in any service. A bare "5 months" is not.
Use this guide with the right tool: Open the Adjusted Age Calculator for corrected age for a child born before 40 weeks gestation. If the question shifts, compare it with the Corrected Age Calculator or the Chronological Age Calculator.
Which one is the real age
Chronological age is the legal and administrative age. It is what appears on the birth certificate, what determines school year in most systems, what a form asking for age means, and what the child will say when asked how old they are.
Adjusted age is a developmental reference point with no legal standing. It exists to make a comparison fair, and it stops being used at some point in early childhood. Using it in a context that expects chronological age — a form, an enrolment, an eligibility check — produces an error that can be hard to unwind.
Keeping both visible
The most robust records show both ages side by side with the gestational age at birth. That way any reader can see the relationship, recalculate if they need to, and understand why a developmental note references a smaller number than the date of birth suggests.
This matters particularly at handover — between a neonatal unit and a community team, between services, or when a family moves. A record showing one age without its label is the point at which a preterm history quietly disappears from the picture.
When adjustment stops
There is no universal cutoff. Practice commonly discusses correction through the first two years, sometimes longer for babies born very preterm, and specific assessment instruments set their own rules that may differ from general practice.
The decision belongs to the clinical team and, where an assessment is involved, to that instrument's manual. What matters for the record is that the point at which correction stopped is written down, so a later reader does not have to work out whether an age was corrected or not.
Worked example
Try it with the dates in front of you. Where the answer sits close to a threshold, treat that as a prompt to check the rule rather than to conclude.
Common mistakes to avoid
- Writing an age without saying which kind. Label every figure. An unlabelled age in a preterm record is ambiguous by two months or more.
- Using adjusted age on a form or an enrolment. Those want chronological age. Adjusted age has no administrative standing.
- Assuming a fixed point where correction stops. Practice varies and instruments set their own rules. Record when it stopped for this child.
Use the right calculator
Three tools cover most of what this guide describes. Each shows its working, so a result can be checked rather than trusted.
Frequently asked questions
Are adjusted and corrected age the same?
In general use, yes. Terminology varies between services, which is why labelling the number matters more than the term.
Which age goes on a nursery or school form?
Chronological age, calculated from the actual date of birth. Adjusted age is not an administrative age.
What is postmenstrual age?
A related measure counted from the last menstrual period rather than from birth, used mainly in neonatal care. It is not interchangeable with corrected age.