About this calculator
This calculator estimates corrected age, also called adjusted age, for a baby born before term. Corrected age helps compare early milestones and growth with the baby’s due-date-based age.
Corrected age is not a diagnosis. Developmental follow-up, growth charts, vision/hearing checks, and specialist advice matter for premature or medically complex babies.
Uses the AAP/HealthyChildren corrected-age method: actual age in weeks minus the number of weeks the baby was born before 40 weeks gestation.
Activated — preterm age arithmetic
Educational estimate only; not a diagnosis, prescription, or treatment plan.
Formula and method
Weeks early = 40 weeks − gestational age at birth. Corrected age = chronological age since birth − weeks early. Results are shown in weeks and approximate months.
Limitations and when not to rely on this result
- Educational estimate only; not a diagnosis, prescription, or treatment plan.
- Result depends on accurate inputs and may not apply to complex medical situations.
- Use clinician judgment, local guidance, and urgent care pathways when symptoms are severe.
Frequently asked questions
What is corrected age? +
Corrected age adjusts a premature baby’s actual age by subtracting how early the baby was born.
How do I calculate weeks early? +
Subtract the gestational age at birth from 40 weeks. For example, a baby born at 32 weeks was about 8 weeks early.
Why use corrected age? +
It can make developmental and growth expectations more realistic for preterm babies, especially in infancy.
When do people stop correcting age? +
Many clinicians use corrected age through about 2 years, though some situations may require longer developmental context.
Can corrected age replace developmental screening? +
No. It is an arithmetic adjustment only. Concerns about milestones, feeding, tone, hearing, vision, or growth should be discussed with the child’s care team.