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CalcChef

Age Calculator

Age calculator: enter a date of birth to get your age in years, months and days, total days alive, days to your next birthday and the weekday you were born on. How it works

Use the Age Calculator

Your age
Select your birth date
Days alive — · Next birthday —

Worked example

Born March 15, 1990: on October 8, 2026 that is 36 years, 6 months and 23 days, or 13,356 days.

How it is counted: whole years first, then whole months, then days. A month is complete when the same day of the month is reached or, if that day does not exist in the month, on the month's last day (January 31 to February 28 is one month; January 31 to March 1 is 1 month and 1 day). Born on February 29: in a non-leap year the birthday is treated as March 1. Hours, minutes and seconds are counted from midnight at the start of the birth date, on the calendar clock (a daylight-saving change does not alter them).

About the Age Calculator

Someone born March 15, 1990 is 36 years, 6 months and 23 days old on October 8, 2026, which is 13,356 days. Age is counted in whole years first, then whole months, then the days left over. Enter a date of birth and this age calculator counts up to today’s date on your device, or to any other date you pick under Age on.

How the age rule handles month ends and February 29

Date of birthAge onAgeDays old
March 15, 1990October 8, 202636 years, 6 months and 23 days13,356
October 9, 1990October 8, 202635 years, 11 months and 29 days13,148
January 31, 1992February 28, 202634 years, 1 month and 0 days12,447
January 31, 1992March 1, 202634 years, 1 month and 1 day12,448
August 31, 2008September 30, 202618 years, 1 month and 0 days6,604
February 29, 2000February 28, 202625 years, 11 months and 30 days9,496
February 29, 2000March 1, 202626 years, 0 months and 0 days9,497
February 29, 2000February 29, 202828 years, 0 months and 0 days10,227

Each row is the calculator’s result for the two dates shown, with every part written out. On screen a zero part is left out (34 years and 1 month); set Age on to the second date to get the same row.

Days old at round ages, for a birth date of March 15, 1990

AgeBirthdayDays oldWeeks old
10March 15, 20003,653521
18March 15, 20086,575939
21March 15, 20117,6701,095
30March 15, 202010,9581,565
40March 15, 203014,6102,087
50March 15, 204018,2632,609
65March 15, 205523,7413,391

For another birth date the day counts can differ by a day or two, because the number of leap days in the span changes. Weeks are whole weeks.

Day milestones, for a birth date of March 15, 1990

Days oldDateAge on that date
1,000December 9, 19922 years, 8 months and 24 days
5,000November 22, 200313 years, 8 months and 7 days
10,000July 31, 201727 years, 4 months and 16 days
15,000April 9, 203141 years, 0 months and 25 days
20,000December 16, 204454 years, 9 months and 1 day
25,000August 25, 205868 years, 5 months and 10 days
30,000May 3, 207282 years, 1 month and 18 days

How to use this tool

  1. Pick your date of birth. The age appears right away, and the hours, minutes and seconds keep counting while the page is open.
  2. Read the years, months and days at the top, then the total days, the weeks, the days to your next birthday and the weekday you were born on.
  3. To find an age on another day, past or future, pick it under Age on. Left on today, the seconds keep counting.
  4. Add a second date under Compare With to see how far apart two birth dates are.
  5. Copy puts the result on your clipboard. Share adds a link that opens the calculator with your date of birth filled in.

Frequently asked questions

How old am I if I was born in 1990?
On October 8, 2026 you are 36 if your birthday falls on or before October 8, and 35 if it comes later in the year. Born January 1, 1990 you are 36 years, 9 months and 7 days old. Born December 31, 1990 you are 35 years, 9 months and 8 days old.
How old was I on a particular date?
Pick that date under Age on. Born March 15, 1990, you were 9 years, 9 months and 17 days old on January 1, 2000, which is 3,579 days, and exactly 18 years old on March 15, 2008. A future date works the same way. A birth date after the Age on date shows a message instead of an age.
How many days old am I?
The calculator shows it under the age as days alive. Born March 15, 1990, you are 13,356 days old on October 8, 2026. It is a plain count of calendar days, with every February 29 in between included.
How is age counted if I was born on the 31st?
A month is complete on the 31st, or on the last day of a month that has no 31st. Born January 31, 1992, you are 34 years, 1 month and 0 days old on February 28, 2026, and 34 years, 1 month and 1 day old on March 1.
I was born on February 29. When is my birthday in a year without one?
The calculator counts it on March 1. Born February 29, 2000, you are 25 years, 11 months and 30 days old on February 28, 2026, and you turn 26 on March 1, 2026. That is this calculator’s convention; the Age in Seconds calculator on this site counts the same birthday on February 28, so the two differ by a day in non-leap years. If a form or a rule you are working to names a date, go by that.
When will I be 10,000 days old?
At 27 years and 4 months, plus 15 to 18 days for any birth date from 1901 to 2071. For a birth date of March 15, 1990 it was July 31, 2017. Under the days-alive figure, the calculator shows your next day milestone and the date it falls on.
Are the hours, minutes and seconds exact?
They count from midnight at the start of your birth date: total days × 24 hours, plus the time on your clock now. 13,356 days is 320,544 hours at midnight. The time of day you were born is not an input, and a daylight-saving change does not add or remove an hour.

Ages for forms, milestones and siblings

A school or clinic form that asks for a child's age in years and months: a child born April 20, 2021 is 5 years, 5 months and 18 days old on October 8, 2026, and the Total Months box shows 65. The same child passes 2,000 days on October 11, 2026, which the line under the days count announces as the next milestone. Within a year of an 18th, 21st or 65th birthday a card counts down the days to it, and an Age on other worlds panel divides your age by a Mars year (1.88 Earth years) and a Jupiter year (11.86), or multiplies it by 12.37 lunar months. The optional Compare with date shows how far apart two birth dates are: March 15, 1990 and January 31, 1992 are 1 year, 10 months and 16 days apart, or 687 days.

How the age is counted

Whole years are counted first, then whole months, then the days left over. A month is complete on the same day of the month as the birth date, or on the last day of a month that has no such day.

Worked example: born March 15, 1990, you are 36 years, 6 months and 23 days old on October 8, 2026. The 36th birthday was March 15, 2026. Six whole months end on September 15, and 23 more days reach October 8.

The totals come from a plain day count:

total days = day number of the Age on date − day number of the birth date

total seconds = total days × 86,400 + seconds since midnight today (the seconds term only when the Age on date is today)

For the example that is 13,356 days, or 1,908 weeks.

  • Born on the 31st: January 31 to February 28 counts as one month, and March 1 is 1 month and 1 day.

  • Born on February 29: in a year with no leap day, the birthday is counted on March 1.

  • Hours, minutes and seconds start at midnight on the birth date. The time of day you were born is not an input, and daylight-saving changes are ignored.

Age on is today unless you pick another date, past or future: born March 15, 1990, you were 9 years, 9 months and 17 days old on January 1, 2000, or 3,579 days. Today's date and time come from your device. Your date of birth is saved in this browser until you press Clear Saved Values.

Fun Fact: You turn 10,000 days old at 27 years and 4 months, plus 15 to 18 days for any birth date from 1901 to 2071; which of the four depends on the month lengths and leap days in between. Someone born March 15, 1990 reached 10,000 days on July 31, 2017.

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