Calculator Inputs
Example Data Table
| Birth Date | Assessment Date | GA at Birth | Chronological Age | Corrected Age |
|---|---|---|---|---|
| 2026-01-01 | 2026-03-12 | 32w 4d | 10w 0d | 2w 5d |
| 2026-01-15 | 2026-03-12 | 35w 0d | 8w 0d | 3w 0d |
| 2026-02-01 | 2026-03-18 | 38w 2d | 6w 3d | 4w 5d |
Formula Used
Corrected gestational age adjusts chronological age by the time an infant was born before 40 completed weeks.
Chronological Age (days) = Assessment Date - Birth Date
Prematurity Adjustment (days) = max(0, 280 - ((Gestational Weeks × 7) + Gestational Days))
Corrected Gestational Age (days) = Chronological Age - Prematurity Adjustment
Postmenstrual Age (days) = Gestational Age at Birth + Chronological Age
A 40-week pregnancy equals 280 days. If birth occurred at term or later, the adjustment becomes zero.
How to Use This Calculator
Enter the infant’s birth date and the follow-up or clinic assessment date.
Provide gestational age at birth using completed weeks and extra days.
Add birth weight if you want it included in the summary export.
Press the calculate button to view corrected age, chronological age, and postmenstrual age.
Use the chart and export buttons for documentation, review, or discussion with caregivers and clinicians.
Important Note
This tool is for estimation and educational support. Growth, feeding, developmental screening, and medical decisions should follow the infant’s care team.
FAQs
1) What is corrected gestational age?
It is the infant’s age after subtracting the number of weeks born before 40 weeks. It helps interpret growth and development more fairly in preterm babies.
2) When should I use corrected age?
Use it during follow-up visits for preterm infants when reviewing developmental progress, feeding, growth, and milestones. Clinical teams often use it during the first months or years.
3) What if the baby was born at term?
If birth occurred at 40 weeks or later, no prematurity adjustment is applied. Corrected age and chronological age will be the same.
4) Why can corrected age become negative?
This can happen when the assessment date is still before the estimated 40-week term-equivalent date. It means the infant has not yet reached full-term age.
5) Is corrected age the same as postmenstrual age?
No. Corrected age adjusts time after birth for prematurity. Postmenstrual age combines gestational age at birth with chronological age after delivery.
6) Should I use gestational age at birth or due date?
Gestational age at birth is usually enough for the calculation. A reliable due date may help clinical review, but the correction still depends on time born before 40 weeks.
7) How long do clinicians usually correct age?
Many clinicians use corrected age in infancy and sometimes up to about two years for developmental interpretation. Practice can vary by setting and clinical purpose.
8) Does this calculator replace medical advice?
No. It is a documentation and estimation aid. Medical decisions should come from qualified clinicians who know the infant’s history and current condition.