Adjusted Age Calculator
Calculate chronological age, corrected age and the term-equivalent date for a baby born prematurely. Enter gestational age at birth or the estimated due date. Corrected age is also called adjusted age.
Developmental planning only: this calculator does not assess growth, diagnose delay or replace your pediatrician or neonatal follow-up team.
Adjusted age formula
Corrected age = chronological age − time born early. When gestational age at birth is known, time born early equals 40 weeks minus gestational age at birth. The calculation uses exact days, so 32 weeks and 4 days remains distinct from 32 weeks.
The American Academy of Pediatrics uses this 40-week baseline for the correction formula even though it notes that full term begins at 39 weeks. A birth before 37 completed weeks is generally considered preterm. Confirm the recorded gestational age and due date with the baby’s clinical team.
Checked examples
| Inputs | Calculated result |
|---|---|
| Born at 32 weeks; chronological age 16 weeks | 8 weeks corrected age |
| Born at 29 weeks; chronological age 16 weeks | 5 weeks corrected age |
| Born 56 days before the estimated due date; chronological age 112 days | 56 days corrected age |
| Born at 35 weeks and 3 days | 32 days early |
How to use the calculator
- Select gestational age if you know the completed weeks and additional days recorded at birth.
- Select estimated due date if that is the reliable information available.
- Enter the birth date and the date on which you want the age calculated.
- Read chronological and corrected age separately; neither should be substituted for clinical assessment.
- Use the calendar only to see when each corrected-age month is reached, not as a promise of a specific milestone.
Important limits
- The result is arithmetic based on the dates entered. It does not evaluate growth, feeding, neurological development or milestone achievement.
- Before the term-equivalent date, the calculator reports the remaining days rather than describing a negative developmental age.
- The American Academy of Pediatrics explains that corrected age is especially useful during the first 2 years. Individual follow-up may differ.
- Gestational age and due dates can be revised clinically. Use the dates documented by the baby’s care team.
- Contact a pediatrician or neonatal follow-up service about development, growth or any health concern.
Clinical references
- American Academy of Pediatrics: Corrected Age for Preemies
- American Academy of Pediatrics: Preemie Growth and Developmental Milestones
- Sydney Children’s Hospitals Network: Corrected Age and Milestones
Related calculators
Use the Age Calculator for general chronological age, the Due Date Calculator for pregnancy dating methods, or the Date Calculator for general calendar arithmetic.