Age seems simple until you need it exactly: for a form that asks for age in months, a milestone birthday, an eligibility cutoff, or just curiosity about how many days you have been alive. This calculator gives the calendar age in years, months and days, then the same span in weeks, days, hours and minutes.
How it is calculated
- Years, months and days are counted the way people do: whole years first, then whole months, then the remaining days. Someone born January 31 is one month old on February 28 (or 29), because February has no 31st. This matches how doctors, schools and courts count age.
- Total days is the plain difference between the two dates, so leap days are included automatically.
- Weeks, hours and minutes are derived from total days. Months for the "in months" line are years × 12 + months.
- Next birthday is the next occurrence of the birth month and day. People born on February 29 get March 1 in non-leap years, the most common legal convention.
Example
Born June 15, 1990, checked on September 14, 2026: 36 years, 2 months and 30 days; 13,240 days; about 1,891 weeks. Born on a Friday. Next birthday in 274 days.
Why age in months matters for babies
Pediatric growth charts and vaccine schedules use months, and "18 months" means exactly 18 calendar months from the birth date, not 78 weeks. Enter the birth date and today, and read the "in months" line.
Age on a specific date
Change the second date to answer questions like "how old will I be on the day of the wedding" or "how old was she when the photo was taken". The calculation is the same, just anchored to that date.
Frequently asked questions
How do I calculate my age exactly?
Count whole years from your birthday, then whole months, then the days left over. The calculator does this from the two dates and also shows the total in days, which is the most precise single number.
How many days old am I?
Enter your birth date above; total days is shown in the result panel. As a rough check, multiply your age in years by 365.25.
What if I was born on February 29?
In years without a February 29 the calculator uses March 1 as your birthday, which is what most countries use legally. Your exact age in days is unaffected.
How is age calculated in months for a baby?
From the birth date, in calendar months: a baby born on the 10th turns one month old on the 10th of the next month. Weeks and months are not interchangeable; 4 weeks is not a month.
Does the calculator account for leap years?
Yes. Total days is the real difference between the dates, and calendar months handle February correctly.
Sources
By Calcelate Team. Formula from the sources above.
- 2026-09-14 · Formula and texts checked