What the Cornell age calculator did
For years, clinicians and therapists used a simple age calculator hosted on a Weill Cornell Medicine web server, in a set of pediatric intensive care calculators. It took a date of birth and a second date (today by default, in US mm/dd/yyyy format) and returned:
- age in whole years plus the remaining months as a decimal,
- total age in months, weeks and days, each rounded to one decimal place.
Behind the scenes it divided the number of days by fixed averages:
days = date − date of birth total months = days ÷ 30.4375 years = whole part of (days ÷ 365.24) months = (days − years × 365.24) ÷ 30.4375
When we checked on 30 October 2026, the original address returned a “Not Found” error, which is why many people now search for an alternative.
Decimal months vs calendar months
Average months are handy for quick clinical arithmetic, but they are not the months on a calendar. Take a child born on 15 March 2019 and seen on 2 October 2024:
| Method | Result | What it means |
|---|---|---|
| Cornell-style decimal | 5 years 6.6 months | 6 average months plus about 18 days |
| Calendar (exact) | 5;6;17 | 5 years, 6 months, 17 days |
Reading “6.6” as “6 months 6 days” is a common slip. For standardized test record forms, always use calendar years;months;days.
Which one should I use?
- Score sheets and test norms: calendar Y;M;D. Use the Chronological Age Calculator, which also copies the result in one tap.
- Preterm babies: the Corrected Age Calculator.
- Matching an old record that used the Cornell tool: the decimal column above reproduces its output.
AgeCountLab is independent and not affiliated with Cornell University or Weill Cornell Medicine.
Frequently asked questions
What was the Cornell age calculator?
A free web form on a Weill Cornell Medicine server (med.cornell.edu), in a section of pediatric intensive care (PICU) calculators, created in October 2000. You entered a date of birth and a second date, and it returned age in years plus decimal months, total months, weeks and days.
Is the Cornell age calculator still online?
When we checked on 30 October 2026, the original page returned a “Not Found” error. Archived copies can still be viewed on the Internet Archive’s Wayback Machine. This page reproduces its decimal output and adds calendar years, months and days.
Why does 6.6 months not mean 6 months and 6 days?
The decimal is a fraction of an average month of 30.4375 days. 0.6 of a month is about 18 days, so 6.6 months is roughly 6 months and 18 days, not 6 months and 6 days.
Which result should I put on a test record form?
Use calendar years;months;days (for example 5;6;17). Decimal months are averages and are not the format standardized test norms use. Our <a href="/chronological-age-calculator/">Chronological Age Calculator</a> is built for score sheets.
Is AgeCountLab affiliated with Cornell?
No. AgeCountLab is independent and is not affiliated with, endorsed by or connected to Cornell University or Weill Cornell Medicine. The name is used only to describe the tool this page is compatible with.