Introduction
When a baby is born early, their age needs a second look. The Adjusted Age Calculator shows you two ages at once: your child's chronological age (the time since birth) and their adjusted age (also called corrected age). Adjusted age takes away the weeks your baby was born early, so you can track growth and skills from their due date instead of their birth date.
Doctors, nurses, and therapists use corrected age to judge milestones like rolling over, sitting, talking, and walking. A baby born at 31 weeks is about 9 weeks early. At 6 months old, that baby may act more like a 4-month-old, and that is normal. Using the wrong age can make a healthy preemie look behind.
Enter your baby's date of birth and pick a date to measure from (today or any other day). Then add the gestational age at birth in weeks and days, or enter the estimated due date instead.
The results include the math, step by step. You also see weeks of prematurity, the due date, charts that compare both ages, and a table of dates when your child reaches key adjusted-age milestones like 18, 24, and 32 months. The calculator flags the common 24-month cutoff too, the point where most doctors stop correcting for prematurity and go back to plain chronological age.
This calculator is a guide, not medical advice. Always talk with your child's doctor about growth and development.
How to use our Adjusted Age Calculator
Enter your baby's birth date, the date you want to check, and how early your baby was born. The calculator shows your baby's chronological age, adjusted (corrected) age, weeks of prematurity, a step-by-step solution, and milestone dates.
Baby's Date of Birth: Pick the day your baby was born. It cannot be a future date.
Calculate Adjusted Age As Of: Pick the date you want the age for. It starts on today's date, but you can change it to a past checkup or a future visit.
Gestational age input method: Choose one way to tell us how early your baby came. Pick "Enter Gestational Age" if you know the weeks and days at birth, or pick "Enter Estimated Due Date" if you only know the due date.
Gestational Age at Birth (Weeks): Choose the number of full weeks your baby had at birth, from 22 to 44 weeks.
Additional Days (0–6): Choose any extra days past those full weeks. For example, 31 weeks and 4 days.
Estimated Due Date (EDD): If you chose the due date method, pick the date your baby was due. The calculator works out the gestational age from the birth date and the due date.
Calculate Adjusted Age: Click this button to see the results, charts, and milestone table. Click Reset / Clear to start over.
What Is Adjusted Age?
Adjusted age (also called corrected age) is a baby's age counted from their due date instead of their birth date. It is used for babies born early (premature). A full-term pregnancy is 40 weeks. If a baby is born at 32 weeks, that baby came 8 weeks early. So at 6 months old, their adjusted age is about 4 months.
Why Adjusted Age Matters
Premature babies need extra time to catch up. Their brains and bodies grow on a schedule closer to their due date. If you compare a preemie to full-term babies the same number of days old, it can look like the baby is behind when they are really right on track.
Doctors and therapists use adjusted age to:
- Check growth on weight, length, and head size charts
- Judge milestones like rolling, sitting, crawling, walking, and talking
- Plan feeding and sleep steps
- Time developmental screenings and follow-up visits
Shots (vaccines) are one big exception. Those are given by chronological age, not adjusted age.
How the Math Works
The math is simple subtraction:
- Find weeks early: 40 weeks − gestational age at birth
- Subtract those weeks from the baby's actual (chronological) age
Example: A baby born at 31 weeks and 4 days was 8 weeks and 3 days early. At 12 months old, their adjusted age is about 9 months and 1 week.
Gestational Age Groups
| Group | Weeks at Birth |
|---|---|
| Extremely preterm | Under 28 weeks |
| Very preterm | 28 to 31 weeks |
| Moderate to late preterm | 32 to 36 weeks |
| Full term | 39 to 40 weeks |
The earlier a baby is born, the bigger the gap between actual age and adjusted age.
When to Stop Correcting
Most doctors stop using adjusted age at 24 months (2 years) corrected. By then, most children born early have caught up, so actual age is used from that point on. Some clinics stop sooner for babies born only a few weeks early, and some keep correcting longer for babies born very early. Follow what your child's doctor says.
Good to Know
Babies born at 40 weeks or later get no correction. Their adjusted age and actual age are the same. Adjusted age is also a guide, not a grade. If you are worried about your child's growth or skills, talk to your pediatrician. Early help works best when it starts early.