How to read the corrected-age timeline
Results show three ages with different purposes. Chronological age starts at birth; corrected age starts at the expected due date. Postmenstrual age adds gestational age at birth to the time since birth. The violet marker shows the assessment date you are exploring.
The calendar marks the dates when a baby reaches 3, 6, 9, 12, 18 and 24 corrected calendar months. Selecting a date updates the three ages and the result link. Months are counted from the expected due date and can have 28 to 31 days.
Copy shares exactly the assessment date displayed on screen. Edit returns to the form with the entered values, and Print prepares a summary. The link works without an account and anyone receiving it can view the dates.
| Gestational age at birth | Chronological age | Corrected age | Postmenstrual age |
|---|---|---|---|
| 28 weeks 0 days | 16 weeks 0 days | 4 weeks 0 days | 44 weeks 0 days |
| 30 weeks 0 days | 16 weeks 0 days | 6 weeks 0 days | 46 weeks 0 days |
| 32 weeks 0 days | 16 weeks 0 days | 8 weeks 0 days | 48 weeks 0 days |
| 34 weeks 0 days | 16 weeks 0 days | 10 weeks 0 days | 50 weeks 0 days |
| 36 weeks 0 days | 16 weeks 0 days | 12 weeks 0 days | 52 weeks 0 days |
Examples use completed gestational weeks with no additional days. This table compares ages; it does not represent an individual baby’s development or growth.
This tool supports births from 20 weeks to 36 weeks and 6 days, and assessment dates up to 3 calendar years after birth. These are calculator limits, not a universal instruction on how long to use corrected age.
AAP parent guidance describes using corrected age to understand development during the first two years. Its growth assessment guidance recommends age correction for children born preterm until age three. These are different uses; the calculator does not apply one universal stopping date or assess developmental delay.