What adjusted age is
Adjusted age, also called corrected age, is your baby's age counted from the due date instead of the birth date. The American Academy of Pediatrics says that during the first 2 years, using your baby's corrected age gives a better idea of when to expect developmental milestones. A baby born 8 weeks early who is 6 months old has an adjusted age of about 4 months.
How it is calculated
- Due date = birth date + (40 weeks − weeks at birth). A baby born at 32 weeks 0 days arrived 8 weeks (56 days) early.
- Adjusted age counts calendar months and days from the due date; actual age counts from the birth date. A date anchored on February 29 counts as March 1 in common years.
- Babies born at 37 weeks or later are not preterm, so no adjustment is shown.
Weeks at birth — when adjusted age reaches 2 years
An adjusted age of 2 years arrives later than the second birthday by as long as the baby was early. These are estimates from this page's formula (one month = 30.44 days — use the calculator for the exact date).
| Born at | Born early by | Adjusted 2 years = actual age |
|---|---|---|
| 24 weeks | 16 weeks (112 days) | about 27.7 months |
| 25 weeks | 15 weeks (105 days) | about 27.4 months |
| 26 weeks | 14 weeks (98 days) | about 27.2 months |
| 27 weeks | 13 weeks (91 days) | about 27 months |
| 28 weeks | 12 weeks (84 days) | about 26.8 months |
| 29 weeks | 11 weeks (77 days) | about 26.5 months |
| 30 weeks | 10 weeks (70 days) | about 26.3 months |
| 31 weeks | 9 weeks (63 days) | about 26.1 months |
| 32 weeks | 8 weeks (56 days) | about 25.8 months |
| 33 weeks | 7 weeks (49 days) | about 25.6 months |
| 34 weeks | 6 weeks (42 days) | about 25.4 months |
| 35 weeks | 5 weeks (35 days) | about 25.1 months |
| 36 weeks | 4 weeks (28 days) | about 24.9 months |
How long to use adjusted age can vary from baby to baby.
What this calculator does not cover
- Growth percentiles, developmental screening, vaccine schedules, or any diagnosis or treatment.
This is a reference tool, not medical advice. Ask your child's pediatrician.
Frequently asked questions
How is adjusted age calculated?
Subtract the time your baby was born early — 40 weeks minus the weeks at birth — from the actual age. The American Academy of Pediatrics gives the example of a baby born at 32 weeks, 8 weeks early. This page counts adjusted age in calendar months and days from the due date.
How long should I use adjusted age?
The American Academy of Pediatrics says that during the first 2 years, corrected age gives a better idea of when to expect developmental milestones. Ask your child's pediatrician about your baby.
What if my baby was born at 37 weeks or later?
Babies born at 37 weeks or later are not considered preterm, so the calculator shows the actual age without an adjustment.
Why does it show days until the due date?
If the due date has not arrived yet, adjusted age has not started. The calculator shows how many days are left until the due date instead.