Age Calculator

How to use the age calculator

Enter a date of birth and, if you like, an "as of" date. By default the second date is today, so the calculator shows your current age, but you can set it to any date in the past or future — for example to check how old someone will be on a wedding day, a retirement date or an exam deadline. The result updates instantly and shows your age in years, months and days, a countdown to your next birthday, the day of the week you were born, and your Western and Chinese zodiac signs.

Open the table to see your age expressed in total months, weeks, days, hours, minutes and seconds, and look at the step-by-step working to see exactly how the figure was reached.

How age is calculated

Most people count age in "completed" years — the number of birthdays that have passed. The calculator follows the same convention used by schools, governments and insurers worldwide:

1. Count how many complete calendar months fit between the birth date and the target date.
2. Divide by 12: the quotient is your age in years and the remainder is extra months.
3. Count the days left over from the last "monthly birthday" to the target date.

Total days are found by counting calendar days between the two dates, which automatically handles leap years. Weeks are total days divided by 7, and hours are days × 24.

Worked example

Take someone born on 15 June 1990 and calculate their age on 3 October 2026. From June 1990 to June 2026 is 36 years. From 15 June 2026 to 15 September 2026 adds 3 more months. From 15 September to 3 October is 18 days. Their age is therefore 36 years, 3 months and 18 days. Counting every day, that is 13,259 days — about 1,894 weeks, or 318,216 hours. They were born on a Friday, and their star sign is Gemini (21 May – 20 June).

Edge cases: month ends and leap-day birthdays

Months have different lengths, which creates some tricky cases. If you were born on the 31st, a month with only 30 days has no matching date, so the calculator treats the last day of that month as your "monthly birthday". For example, from 31 January to 1 March is counted as 1 month and 1 day, because 28 (or 29) February is the end of the first month.

People born on 29 February — "leaplings" — only see their exact birthday every four years. Legal rules differ by country: some jurisdictions treat 28 February as the birthday in common years and others use 1 March. This calculator uses 28 February, which is the most common convention for everyday purposes. If you need the legal date for a specific country, check the local rule.

Where exact age matters

• School admissions and sports leagues often use an age on a fixed cut-off date — set the "as of" field to that date.
• Retirement and pensions depend on age in years and months. Pair this tool with our retirement calculator to plan savings.
• Health and development: pediatric growth charts use age in months, and many health formulas such as the BMR calculator need age in years.
• Visas, licences and contracts often require a minimum age on the application date.

To count the days between any two events rather than a birth date, use the days between dates calculator. To find what weekday a historical date fell on, try the day of the week calculator.

Different ways the world counts age

The international standard counts completed years from birth. Historically, the traditional East Asian system counted a newborn as one year old and added a year every Lunar New Year, so a person could be one or two years "older" than their international age. South Korea officially standardised on the international method for legal and administrative purposes in 2023. When comparing ages across cultures, make sure you know which system is being used.