How to calculate your age
- Enter the Date of birth. You can type it, or open the calendar and jump straight to a year with the year list.
- Age on this date starts at today. Change it to see how old someone was on a past date, or will be on a future one.
- Read the results: the exact age in years, months and days; the totals in months, weeks, days and hours; the weekday of the birth date; and the next birthday with how many days are left and the age that will be reached.
How the exact age is worked out
The calculator counts complete calendar months from the date of birth, turns every twelve of them into a year, and then counts the days left over. A month is complete when the same day number comes round again. When a month doesn’t have that day – someone born on the 31st in a 30-day month, for example – the month is complete on its last day instead.
Because months have different lengths, the days part depends on the month just before the chosen date. For someone born on 6 November 1999, the day before their 27th birthday shows 26 years, 11 months and 30 days, since that October had 31 days.
The totals are straightforward counts. Total days counts every calendar day from the birth date to the chosen date, including each 29 February in between; Total weeks is the number of complete weeks; and Total hours is simply the days times 24, so it is approximate – it doesn’t know the time of birth or about clock changes.
Worked examples
- Born 15 June 1995, age on 5 November 2026: 31 years, 4 months and 21 days. That is 376 months, 1,638 weeks or 11,466 days. The birth date was a Thursday, and the next birthday, 15 June 2027, is 222 days away, when this person turns 32.
- Born 31 January 2000: on 28 February 2000 the age is 0 months and 28 days; on 29 February 2000 (a leap year) it is exactly 1 month, because February has no 31st; on 30 March 2000 it is 1 month and 30 days; and on 31 March 2000, 2 months.
- Starting school: a child born on 1 March 2020 is 6 years and 6 months old on 1 September 2026. Age limits for school entry, sports categories or insurance usually refer to a fixed cut-off date, so enter that date rather than today.
Birthdays on 29 February
In years without a 29 February, this calculator counts 28 February as the birthday. Someone born on 29 February 2004 is shown as exactly 21 on 28 February 2025, with a happy-birthday message, and their next birthday after that is listed as 28 February. Legal rules for leap-day birthdays differ between countries – some treat 1 March as the birthday in common years – so check the local rule when an exact legal date matters.
Different ways of counting age
This calculator uses the international system: you are 0 at birth and a year older on each birthday. It is the system used in law in almost every country today, but it isn’t the only one.
- Traditional East Asian age counts a baby as 1 at birth and adds a year at the new year rather than on the birthday, so it can be up to two years more than the international age. South Korea switched to the international age for legal and administrative purposes in June 2023, and Japan and China also use completed years in law, but the traditional count still appears in everyday conversation.
- Year-based age is the current year minus the year of birth, ignoring the birthday. Some rules and sports competitions use it so that everyone born in the same year is treated alike.
Other uses
- Babies and toddlers: development is usually described in months, so the Total months figure is the number to look at.
- Anniversaries and milestones: the age of a company, a building, a pet or a relationship works exactly like a person’s age.
- Historical dates: enter two past dates to find out how old someone was when an event happened.
- Day-count milestones: someone born on 15 June 1995 was 10,000 days old on 31 October 2022. To find dates like this, add days to a date with the Date Calculator.
FAQ
Why isn’t my age in days simply my age in years times 365?
Because of leap years. Every 29 February since you were born adds one extra day, and the leftover months and days have their own real lengths.
Does the time of birth matter?
No. The calculator works with whole calendar days, so you become a year older at the start of your birthday, wherever you are.
What day of the week was I born?
See the Born on row under the results; it gives the full date with the weekday.
Can I count the time between any two dates, not just from a birthday?
Yes, enter the earlier date as the date of birth. If you also want weekdays, weekends, or to add and subtract days from a date, the Date Calculator is built for that.