Age Calculator
Calculate exact age in years, months, and days from date of birth.
By Syed Mubashir Ali · Last updated
How your age is worked out
The calculator counts whole years first, then whole months, then the days left over: the same way people give their age out loud. A month is counted once the same day number comes round again. When the next month is too short to have that day (born on the 31st, say), the month is counted from the day after that short month ends. Born on 31 January, you're 28 days old on 28 February and 1 month and 1 day old on 1 March, whether or not it's a leap year.
The totals are other ways of measuring the same span, not parts of the age. Total days counts every day from the date of birth up to the 'as of' date, so it's 0 on the day itself and 1 the next day. Total weeks is those days in whole weeks, total months is 12 for every year plus the months over, and hours and minutes are the days multiplied out. Everything runs midnight to midnight, which is why the time of birth makes no difference.
Change Calculate Age As Of to any date, earlier or later, and the whole result is worked out for that day instead: an age on the closing date of an application, at the start of a school year, or at a wedding fifty years ago. Next birthday follows the 'as of' date too.
Birthdays on 29 February
A leap-day birthday only comes round every four years, so the calculator has to pick a day for the other three. It uses 1 March, the first day after 28 February: that's when the years figure goes up and the date shown under Next birthday. In a leap year, 29 February is the birthday as usual.
Not everyone draws the line in the same place. Some organisations and computer systems treat 28 February as the birthday in common years, and the rules for official ages, such as when you can drive or sign a contract, are set country by country. When a particular day matters, check which one the form or the organisation uses. Then set the 'as of' date to 28 February and 1 March in turn, and you'll see both answers.
How to Use Age Calculator
- 1Enter your date of birth using the date picker.
- 2The 'Calculate Age As Of' field defaults to today. You can change it to calculate age at any past or future date.
- 3Click 'Today' to reset the reference date to the current date.
- 4Your exact age in years, months, and days appears instantly, along with totals in days, weeks, months, hours, and minutes.
- 5Your next birthday date and days until it are shown at the bottom.
Frequently Asked Questions
How is the exact age calculated?
The calculator counts complete years, then remaining complete months, then remaining days. It correctly handles varying month lengths and leap years. For example, from January 31 to March 1 is 1 month and 1 day (in a non-leap year) because February has 28 days.
Can I calculate age as of a past or future date?
Yes. Change the 'Calculate Age As Of' date to any date to see what the age was or will be on that specific day. This is useful for legal age verification, historical research, or checking if someone is old enough for a particular milestone.
Why might my age differ by a day from what I expect?
Age calculation can vary by one day depending on whether you count the birthday itself as day zero or day one. Our calculator counts the birthday as day zero: meaning on your birthday, days = 0, months = 0, years = N (a new year). This matches the most common legal and medical convention.
How are total hours and minutes calculated?
Total hours = total days × 24. Total minutes = total hours × 60. These are approximate values based on full days. They do not account for the exact time of birth.
What if I was born on 29 February?
In years without a 29 February, the calculator moves your birthday to 1 March: that's the day the years figure goes up and the date Next birthday counts down to. Someone born on 29 February 2000 is shown as 24 years, 11 months and 30 days on 28 February 2025, and 25 from 1 March. If a form uses 28 February instead, set the 'as of' date to each and compare.
Which date does it use as today?
Your device's own date, in your time zone, so someone in Sydney and someone in London can see different ages for a few hours either side of midnight. Click Today to come back to it after changing the 'as of' date.
Can I send the result to someone?
Copy result puts the age and the totals on your clipboard as text. Share copies a link that opens the calculator with the same date of birth. The 'as of' date is only in the link if you changed it, so a link sent today still works out the age on the day it's opened.
About Age Calculator
The Age Calculator computes your exact age in years, months, and days, along with a full set of time-based metrics including total days lived, total weeks, total hours, and total minutes. It's a surprisingly useful tool for many practical and curious purposes.
The most common use is simply verifying or checking someone's exact age for legal, medical, or official purposes: such as confirming eligibility for age-restricted activities, verifying passport or license renewal dates, or completing forms that require age at a specific date rather than current age.
The calculator handles all the complexity of calendar arithmetic correctly. It accounts for months of different lengths (28, 29, 30, or 31 days), correctly handles leap years (February 29 birthdays), and uses the conventional age calculation method where age increments on the anniversary of the birth date.
The 'Calculate As Of' date feature is especially useful for historical or planning purposes. Historians can calculate how old a historical figure was on a particular date. Parents can calculate exactly how old a child will be on their first day of school. HR professionals can calculate years of service. The tool handles all of these scenarios with the same precision.