Corrected age
Understand chronological and corrected age.
See examples and explanations ↓Corrected age is a date adjustment for understanding development. It does not determine which growth reference applies.
Time together
Enter dates, then select Calculate.
What this tool explores
Compare time since birth with age adjusted to a 40-week reference using gestational age at birth. Negative values before the calculated due date stay visible so the two date conventions remain distinct.
Step by step
- Enter the birth and reference dates. Elapsed days start at zero on the birth date.
- Enter gestational weeks and additional days separately from the birth record. For 32 weeks 4 days, enter 32 and 4, not 32.4 weeks.
- After calculating, read chronological days, corrected days and the calculated due date together. Supported gestational inputs run from 22 weeks 0 days through 36 weeks 6 days.
What to look for in these results
The main week and month counts are chronological age since birth; corrected days appear separately. Corrected age does not replace chronological age. The result is not automatically used as the age for a growth percentile or an individual care schedule.
Questions about this tool
Why enter the additional gestational days?
32 weeks 4 days equals 228 days, so the adjustment is 52 days. Omitting the four days changes the adjustment to 56 and shifts corrected age by four days. Enter the weeks and days recorded at birth.
How should I read a difference from the recorded due date?
The displayed due date is calculated arithmetically from the birth date and entered gestation. It does not update a due date in clinical records. Check the inputs and follow the care team’s guidance for clinical use.
Saving inputs on this device
Select Remember on this device and calculate to save inputs. On your next visit, only inputs are restored; results wait for the Calculate button. Saving is off by default. Other people using a shared device may see saved inputs.
Date conventions
Elapsed days use calendar-date differences, with birth as day zero, independent of 23- or 25-hour daylight-saving days. Completed months advance on the matching day, or the last day when a month is shorter. For example, January 31 to February 29, 2024 is 29 elapsed days and one completed month.
The 50th, 100th, 200th, and 300th day milestones count birth as day one. The 100th day is one day before 100 full days have elapsed. Input dates range from 1900 through 2100 and the reference date must fall from birth through the exact 24-month anniversary. Out-of-range inputs are rejected.
Corrected-age method and example
Corrected age in days = chronological days − [280 − gestational days at birth]. A baby born at 32 weeks and now 16 weeks after birth has a corrected age of eight weeks. Values before the calculated due date remain negative. The supported 22-week to 36-week-6-day input range is a software boundary, not a viability or clinical decision threshold.
This formula does not determine growth-chart applicability. Percentiles require separately verified reference data and eligibility rules. The AAP developmental guidance and example were checked; this is not medical expert review.
AAP HealthyChildren — Corrected Age for Preemies · Source review date: 2026-10-05
Frequently asked questions
Do I need a birth time or time zone?
This tool counts the difference between two selected calendar dates, not the exact elapsed hours. It does not request a birth time or timezone. Check the reference date yourself.
Can I calculate if storage fails?
Yes. Calculations work in memory. Device storage is optional, and a message explains when it is unavailable.
baby-dates-1.0.0 · Calculation review date: 2026-10-05