About the Age Calculator
This age calculator works out exactly how old someone is on any date. Enter a date of birth and the date you want to measure to — today, a past date or a future one — and it returns the age in completed years, months and days, the same way ages are stated on forms, school admissions and insurance applications.
Beyond the headline age it shows the total number of months, weeks, days and hours lived, the weekday you were born on, and how many days remain until your next birthday. That makes it handy for eligibility cut-offs ("must be 18 by the start date"), retirement and pension planning, milestone parties like 10,000 days old, or simply answering "how old am I?".
Ages are counted in whole calendar months, so month lengths and leap years are handled correctly. For people born on 29 February, birthdays in common years are taken as 28 February, which is the convention used by many (but not all) jurisdictions.
How to use the age calculator
- 1Enter the date of birth.
- 2Set the “age on” date — today for your current age, or any past or future date.
- 3Read your exact age in years, months and days.
- 4Check the totals in months, weeks, days and hours in the table.
- 5Note the countdown to your next birthday and upcoming day-count milestones.
Formula and method
The calculator first counts completed years: the difference between the two calendar years, reduced by one if the birthday has not yet occurred in the “age on” year. It then counts whole calendar months from your most recent birthday, and finally the leftover days. When a month has no matching day (a birthday on the 31st, say), the month is taken to end on its last day (so 31 January to 1 March is 1 month and 1 day), which keeps the day count from ever going negative.
Total days is the exact number of calendar days between the two dates (leap days included), and weeks, hours, minutes and seconds are derived from it. The next-birthday countdown uses 28 February for 29 February birthdays in common years.
- Years
- Completed birthdays up to the “age on” date
- Months
- Whole calendar months since the last birthday
- Days
- Remaining days after the whole months
Worked examples
Born 15 June 1990, age on 29 Sep 2026
From 15 June 1990 the person has had 36 birthdays by 29 September 2026. From 15 June to 15 September is 3 whole months, and 15 to 29 September is 14 more days. That is 13,255 days in total, and the 37th birthday is 259 days away.
Child born 1 March 2019, age on 1 January 2027
The child turned 7 on 1 March 2026 and has had 10 further whole months (to 1 January 2027), so they are exactly 7 years 10 months. They have lived 2,863 days and turn 8 in 59 days.
Leap-day birthday: 29 Feb 2000, age on 28 Feb 2027
Because 2027 is not a leap year, the birthday is treated as 28 February, so on that day the person turns 27. They have lived 9,861 days since 29 February 2000.
Frequently asked questions
How do I calculate my exact age?+
Subtract your birth year from the current year, then subtract one if your birthday has not happened yet this year. Count whole months since your last birthday and then the leftover days. This calculator does all of that automatically, including leap years.
How many days old am I?+
Your age in days is the number of calendar days between your date of birth and today. Someone who is exactly 30 has lived about 10,957 days (30 × 365 plus 7 or 8 leap days). The total-days result shows your exact figure.
When is a leap-day baby’s birthday in non-leap years?+
There is no single rule. Many people celebrate on 28 February and some on 1 March; legal rules differ between countries, with some treating 1 March and others 28 February as the birthday in common years. This tool uses 28 February; check local law for legal age cut-offs.
Does the calculator count the day of birth?+
No. Like a normal age, the count starts at zero on the day you are born and increases by one day at each midnight after that. On your first birthday you are 365 (or 366) days old.
Can I calculate someone’s age on a past or future date?+
Yes. Change the “age on” date to any date — for example a school entry cut-off, a retirement date or a historical event — and the calculator shows the age at that moment.
Why does my age in months differ from years × 12?+
Total months counts every completed calendar month since birth, so it includes the months since your last birthday. At 36 years and 3 months you have lived 435 whole months, not 432.