# Corrected Age Calculator – Adjusted Age for Preemies > Calculate your premature baby's corrected (adjusted) age from birth date and gestational age. Free preemie age calculator with WHO preterm bands and milestones. - **Category:** Date & Time - **Interactive calculator:** https://youcalc.com/en/date-time/corrected-age/ - **Price:** Free, no sign-up required ## Overview A baby born early is, in development terms, younger than the calendar says. Corrected age (also called adjusted age) accounts for that head start the baby never got: it is the age the baby would be if they had been born on their original due date. Doctors use it so a premature baby's growth and milestones are judged fairly — against where they are developmentally, not against full-term babies of the same birth date. This calculator takes the baby's date of birth and either the gestational age at birth (for example 32 weeks and 0 days) or the original estimated due date, plus an assessment date (today by default), and works out both the chronological (actual) age and the corrected age, in weeks-and-days and in months-and-days. ## How to read your result The headline is the corrected age — use this when tracking developmental milestones and plotting growth charts. Beneath it, the chronological (actual) age is the plain time since birth, and "weeks born early" is how much is subtracted to get the corrected age. The WHO band labels how early the baby arrived (extremely, very, or moderate-to-late preterm, or term). The "correction applies" line tells you whether the adjustment is still clinically relevant: by convention it is used until about 2 years of age (extended to about 3 years for extremely preterm babies born before 28 weeks), after which most children have caught up with their full-term peers. ## Method The full-term baseline is 40 weeks (280 days). Weeks born early = 40 weeks − the gestational age at birth; in due-date mode it is the due date minus the birth date, never below zero. Chronological age = assessment date − birth date. Corrected age = chronological age − weeks born early, clamped at zero (if the assessment date is before the original due date, the corrected age shows 0, because the baby has not yet reached its term-equivalent age). Weeks-and-days simply divide the day count by seven; months-and-days are calendar-accurate, with the corrected-age clock starting at the due date so each month keeps its real length. The WHO preterm subcategory comes from the completed weeks of gestation: extremely preterm below 28 weeks, very preterm from 28 to under 32 weeks, moderate-to-late preterm from 32 to under 37 weeks, and term at 37 weeks or more. ## Example - **Setup:** A baby born on 1 January 2024 at 32 weeks and 0 days, assessed on 22 April 2024. - **Result:** The baby is 16 weeks and 0 days old chronologically (112 days). Born at 32 weeks, they arrived 8 weeks (56 days) early — moderate-to-late preterm. Subtracting those 8 weeks gives a corrected age of 8 weeks and 0 days (about 1 month and 27 days). Because the corrected age is well under 2 years, milestones should be tracked against the corrected age, not the actual age. ## Frequently asked questions ### What is corrected (adjusted) age? Corrected age is your baby's chronological age minus the number of weeks they were born early, based on a 40-week full-term pregnancy. It estimates the age the baby would be if they had been born on their due date, which is a fairer basis for judging development. For example, a 4-month-old born 2 months early has a corrected age of about 2 months. ### How long should I use corrected age? Most clinicians use corrected age until about 2 years of age for assessing growth and developmental milestones. For babies born extremely preterm (before 28 weeks), some teams continue to about 3 years. After that point most children have caught up with full-term peers, and chronological age is generally used. Always follow the guidance of your own paediatric team. ### Do I use the gestational age or the due date? Either works — they describe the same thing. If you know the gestational age at birth (such as 32 weeks and 0 days), use that; if you only have the original estimated due date, use due-date mode. Both compute the same number of weeks born early, so the corrected age is identical. ### Is this a substitute for medical advice? No. This calculator is an educational tool that applies the standard 40-week corrected-age convention and the WHO preterm categories. It does not account for individual medical circumstances. Use it to understand the method, but always rely on your paediatrician or neonatal team for decisions about your baby. ## Related calculators - [Age Calculator](https://youcalc.com/en/date-time/age-calculator/) - [Age Gap Calculator](https://youcalc.com/en/date-time/age-gap-calculator/) - [Your Age in 8 Calendars](https://youcalc.com/en/date-time/multi-calendar-age/) - [Hijri Age Calculator](https://youcalc.com/en/date-time/hijri-age/) ## Sources - https://www.healthychildren.org/English/ages-stages/baby/preemie/Pages/Corrected-Age-For-Preemies.aspx - https://www.who.int/news-room/fact-sheets/detail/preterm-birth --- Interactive version: https://youcalc.com/en/date-time/corrected-age/ · From YouCalc — https://youcalc.com