Corrected Age for Preterm Babies
Treat 40 weeks as full term and subtract the weeks missed from the current age. Born at 32 weeks and now 20 weeks old means subtracting eight, for a corrected age of 12 weeks. Developmental milestones should be read against this figure.
Your numbers
Corrected age (wk)
12wk
Difference
8wk
Months
2.8mo
What it means
Corrected age is 12 weeks (about 2.8 months) — read milestones against this.
Formula
Corrected age (wk) = Weeks since birth − (40 − Gestation at birth)
Corrected age is generally used until about two years, after which the gap closes and actual age applies.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Gestation at birth (wk)Gestational age at birth; 40 weeks is full term. | 32 | 22 ~ 42 |
| Weeks since birth (wk)How many weeks since birth. | 20 | 0 ~ 200 |
Step by step
Quick reference table
Results when only Gestation at birth (wk) changes and everything else stays put.
| Gestation at birth (wk) | Corrected age (wk) (wk) | Difference (wk) | Months (mo) |
|---|---|---|---|
| 22 | 2 | 18 | 0.5 |
| 24 | 4 | 16 | 0.9 |
| 32 | 12 | 8 | 2.8 |
| 42 | 22 | -2 | 5.1 |
What each result means
| Result | At default values |
|---|---|
| Corrected age (wk) (wk)Age with the missed weeks removed; read development against this. | 12 |
| Difference (wk)The gap between two values — a quantity, not a rate. | 8 |
| Months (mo)The period counted in months; a yearly rate gets divided by twelve. | 2.8 |
Common mistakes
Corrected age is generally used until about two years, after which the gap closes and actual age applies.
Glossary
- Gestation at birth
- Gestational age at birth; 40 weeks is full term.
- Weeks since birth
- How many weeks since birth.
- Corrected age (wk)
- Age with the missed weeks removed; read development against this.
- Difference
- The gap between two values — a quantity, not a rate.
- Months
- The period counted in months; a yearly rate gets divided by twelve.
Frequently asked questions
Q. How is Corrected Age for Preterm Babies calculated?
Corrected age (wk) = Weeks since birth − (40 − Gestation at birth) — Treat 40 weeks as full term and subtract the weeks missed from the current age. Born at 32 weeks and now 20 weeks old means subtracting eight, for a corrected age of 12 weeks. Developmental milestones should be read against this figure.
Q. Can you walk through an example?
With Gestation at birth 32wk, Weeks since birth 20wk, the answer is Corrected age (wk) 12wk.
Q. What do I need to enter?
Enter Gestation at birth, Weeks since birth. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Gestation at birth (wk) moves the answer to Gestation at birth (wk) 22 → Corrected age (wk) (wk) 2 and Gestation at birth (wk) 42 → Corrected age (wk) (wk) 22. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Corrected age is generally used until about two years, after which the gap closes and actual age applies.
Related calculators
These calculators help you understand health figures; they do not replace diagnosis or prescription. See a clinician if you have symptoms.