Adjusted Age Calculator
HealthCalculate a premature baby's adjusted (corrected) age from chronological age and gestational age at birth. A standard reference used for growth and development tracking.
Adjusted (Corrected) Age
12
Correction Applied
8
What is a Adjusted Age?
The Adjusted Age Calculator computes a premature baby's corrected age by subtracting the number of weeks born early from their chronological age. This gives a more meaningful reference point for tracking growth and developmental milestones in babies born before full term.
This pairs with the Baby Percentile Calculator and Birth Weight Percentile Calculator for a fuller picture of premature infant growth tracking.
How to use this Adjusted Age calculator
- Enter your baby's chronological age in weeks (time since actual birth).
- Enter the gestational age at birth in weeks (how many weeks pregnant you were at delivery).
- Read the Adjusted (Corrected) Age result instantly.
- Use this adjusted age when comparing growth or milestones against typical full-term reference charts, generally until around age 2.
Formula & Methodology
Correction (weeks) = 40 − Gestational Age at Birth (weeks) Adjusted Age = Chronological Age − Correction Worked example — a baby now 20 weeks old, born at 32 weeks gestation: Correction = 40 − 32 = 8 weeks Adjusted Age = 20 − 8 = 12 weeks This means the baby's growth and development are best compared to a 12-week-old full-term baby, not a 20-week-old one.
Frequently Asked Questions
Adjusted age, also called corrected age, is a premature baby's age calculated from their original due date rather than their actual birth date. It subtracts the number of weeks born early from the baby's chronological age, giving a more accurate reference point for growth and development tracking.
A baby born several weeks early is developmentally younger than a full-term baby of the same chronological age, so comparing a premature baby's growth and milestones against their adjusted age gives a fairer, more meaningful comparison than using chronological age alone.
The calculator subtracts the number of weeks the baby was born before 40 weeks (full term) from the baby's current chronological age in weeks, giving the adjusted age.
Many pediatricians recommend using adjusted age for growth and developmental tracking until around 2 years of age, after which the gap between chronological and adjusted age becomes proportionally less significant.
This calculator uses 40 weeks of gestation as the full-term reference point, which is the standard reference used in most adjusted age calculations.
No — adjusted age correction is specifically for babies born preterm (before 37-40 weeks); babies born at or after full term don't need this adjustment since their chronological and gestational timelines already align.
When using growth charts like the [Baby Percentile Calculator](/baby-percentile-calculator/), pediatricians often recommend entering a premature baby's adjusted age rather than chronological age for a more accurate percentile comparison until around age 2.
The numerical gap between adjusted and chronological age stays constant (equal to how early the baby was born), but as a baby gets older, that fixed gap becomes a smaller proportion of their overall age, which is part of why the adjustment becomes less emphasized after age 2.
The [Birth Weight Percentile Calculator](/birth-weight-percentile-calculator/) uses gestational age at birth directly rather than adjusted age, since it's specifically comparing weight at the moment of birth against gestational age at that same moment.
Many pediatricians default to using adjusted age for preterm babies' growth and milestone discussions, but it's worth confirming with your specific provider which age reference they're using for consistency in tracking.
Also known as