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Calculate corrected age for premature babies: enter birth date, due date, and today to see adjusted vs chronological age, weeks born early, and when most guidelines suggest stopping correction (~24 months from due date). Use results for milestone and growth-chart expectations — not for vaccines or legal age.
Last updated: June 4, 2026
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Date when baby was actually born
Expected due date (40 weeks gestation)
Today's date or date of developmental assessment
Adjusted (Corrected) Age
2 months, 2 weeks
Use this age for developmental milestones
Chronological Age:
4 months
Weeks Premature:
6 weeks
Adjusted Age Details:
Stop Correcting Age At:
See calculator (24 mo adjusted)
(24 months adjusted age - typical guideline)
Development Guidance:
Late preterm (6 weeks early). Use corrected age for milestones and growth until ~12–18 months; follow your pediatrician.
Key Points:
How long to use adjusted age depends on how early your baby was born. Always follow your NICU or pediatric team’s plan.
Due-date age
Chronological age minus weeks born before due date
6–18 mo adjusted
Often catch up quickly
24–36 mo adjusted
Longer correction & follow-up
| Category | Gestational age | Typical weeks early | Correct until (typical) |
|---|---|---|---|
| Late preterm | 34⁰–36⁶ weeks | 1–6 weeks | Often 6–12 months adjusted; some use to 18 mo |
| Moderate preterm | 32⁰–33⁶ weeks | ~4–8 weeks | Typically 18–24 months adjusted |
| Very preterm | 28⁰–31⁶ weeks | ~8–12+ weeks | 24 months adjusted; some NICU teams to 36 mo |
| Extremely preterm | <28 weeks | 12+ weeks | 24–36 months adjusted; close developmental follow-up |
Default calculator scenario (birth date ~4 months ago, due date 6 weeks later):
Adjusted age
~2½ mo
Chronological
~4 mo
Weeks early
6 wk
At adjusted ~2½ months, expect social smiling and head control in tummy time — not full 4-month chronological milestones yet.
| Topic | Use which age? | Notes |
|---|---|---|
| Motor milestones (roll, sit, walk) | Adjusted / corrected age | CDC/AAP expect preemies to be compared to peers at same post–due-date age |
| Language & social milestones | Adjusted age | Reduces false “delay” labels when baby was born weeks early |
| WHO/CDC growth charts (after discharge) | Adjusted age until ~24 mo | Plot weight, length, head circumference at corrected age |
| Feeding & sleep expectations | Adjusted age | Wake windows and solids readiness align with corrected timeline |
| Immunizations | Chronological age | Vaccine schedules use actual birth date per CDC |
| Medication dosing | Chronological age (or weight) | Prescriptions follow birth date and weight, not corrected age |
| Daycare / school enrollment | Chronological age | Legal age for programs uses birth certificate date |
Pediatricians and NICU follow-up clinics use the same date math as this tool. For pregnancy dating before birth, pair with our gestational age calculator and medical calculators.
Stop correcting at 24 months after the due date is a common rule of thumb; your team may shorten or extend that for extremely preterm infants.
Educational disclaimer
This calculator supports learning and parent questions — it does not diagnose developmental delay or replace NICU follow-up, ASQ screening, or your pediatrician’s exam. If skills are missing at corrected age, ask about early intervention (IDEA Part C before age 3 in the U.S.).
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