A little clarity, every day
Two clearly labelled ages, side by side. Enter your due date or precise gestational weeks and days.
Add a birth date to see exact calendar months, weeks and days, plus the next dates worth remembering.
Chronological age starts at birth. Corrected age starts at the expected due date. Our corrected mode keeps the two results together, including exact weeks and days, so you can see the adjustment rather than replace one age with another.
4 × 7. Always.
The month and year decide.
Four weeks can line up with one calendar month in a particular example, but it is not a conversion rule. Fifty-two weeks is 364 days, so it is not exactly twelve calendar months either.
Why weeks and months do not matchReproducible examples, with the counting rules visible.
Birth January 1 → assessment April 23, 2025
112 elapsed days = 16 weeks. The 40-week reference is 56 days after birth, on February 26. Corrected age on April 23 is 56 days = 8 weeks. These weeks are not converted into calendar months.
32 weeks + 3 days at birth; assessed 16 weeks later
The adjustment is 280 − 227 = 53 days, not 56. Subtract 53 from 112 elapsed days: corrected age is 59 days, or 8 weeks and 3 days. Rounding the gestation to 32 weeks would lose three days.
Birth January 1; due February 26; assessed February 19, 2025
Chronological age is 49 days, or 7 weeks. We show “7 days until the due date” instead of a negative corrected age. On February 26, corrected age starts at 0 days.
Celebration dates here use the birth date. Corrected age is displayed separately and does not move your baby’s birthday or replace their chronological age.
A date milestone marks time. It does not say when a baby should walk, talk, or reach another skill.
Use the visible corrected-age mode for a baby born early. Enter either the original expected due date or completed gestational weeks plus 0–6 extra days.
Elapsed time from the birth date to the assessment date. It stays visible in both modes.
Elapsed time from the expected due date to the assessment date. Before that date, the tool shows a countdown.
Corrected days = elapsed days − (280 − gestational days at birth)
The formula uses 40 weeks (280 days) as a calculation reference. That reference does not define the only medical meaning of “full term.” Ask your baby’s clinician how corrected age applies to their care.
Read the chronological vs. corrected age guideKeep developmental checklists separate from celebration dates. These external resources explain their own age categories and limitations.
CDC publishes infant checklists at 2, 4, 6, 9, and 12 months—not for every month. Visit the source to choose an available checklist.
Parent guidance about using corrected age in the first two years. Your baby’s clinician can explain its use in their individual care.
This calculator cannot screen for developmental delay. If you have concerns, discuss them with your baby’s clinician; a date calculation cannot assess a skill or predict its arrival.
They have different start dates: birth for chronological age, expected due date for corrected age. The tool displays both. The corrected result is information to discuss with your clinician, not a developmental assessment.
Yes. Enter 32 completed weeks and 3 additional days. The tool keeps all three days in the calculation. Additional days must be an integer from 0 to 6.
The chronological age still shows normally. Instead of presenting a negative corrected age, we show the days remaining until the due date. Corrected age starts at 0 days on that date.
Forty weeks is the reference used by this corrected-age formula. It is a calculation convention, not a statement that “full term” has only one medical definition.
The calculator works in your browser. It does not put entered dates into a URL or send them to a calculation service. Copying or printing creates a copy you control. Saving on this device is optional.
No. This calendar marks elapsed age and date anniversaries. It cannot diagnose delay, assign a developmental score, or predict the date of a particular skill. Use appropriate clinical guidance for developmental questions.