Corrected Age Calculator for Premature Babies

Calculate the corrected age of a premature baby — the age adjusted for weeks born early.

Informational content. This tool does not replace advice from a qualified professional. Use the results as a reference only.

How to use

  1. Enter the baby's date of birth and the gestational age at birth in weeks.
  2. Click Calculate to see both the chronological and corrected age.
  3. Use the corrected age for developmental milestone comparisons until 2 years of age.

About this tool

A baby born at 32 weeks is 8 weeks early. At 4 months of chronological age, the corrected age is about 2 months — and the developmental milestones that matter are the ones for 2 months, not 4.

Corrected age is chronological age minus the number of weeks born before 40 weeks (full term). Paediatricians use it until the child is 2 years old for motor and cognitive milestones, and until 3 years for some growth charts.

This is an informational tool, not a medical assessment. Every premature baby is different, and the paediatrician who follows the child is the one who interprets the milestones in context.

The formula

Corrected age = chronological age − (40 − gestational age at birth) weeks.

Frequently asked questions

Until what age should I use corrected age?

Most paediatricians use it until 2 years for developmental milestones. After that, the difference matters less.

Does corrected age apply to growth charts?

Yes — the WHO growth charts should use corrected age for premature babies until at least 2 years.

Is this medical advice?

No — it is a calculation tool. The paediatrician who follows your child is the one to interpret the milestones.

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