Step-by-step guide: How to Calculate Exact Age in Years, Months and Days
How to use the Age Calculator
- Enter the date of birth.
- The second date is today by default. Change it to find someone’s age on a specific date in the past or future.
- Read the exact age in years, months and days, and the totals in months, weeks and days.
- Check the next birthday and how many days remain until it.
Example: age on an application deadline
An applicant born on 17 May 1990 wants to know their age on 1 March 2026, the deadline for a programme with an age limit of 36.
From 17 May 1990 to 17 May 2025 = 35 years
17 May 2025 to 17 February 2026 = 9 months
17 February 2026 to 1 March 2026 = 12 days
Age on the deadline: 35 years, 9 months and 12 days — under 36.
How the age is calculated
The calculator counts complete calendar years first, then complete months, then the remaining days — the same way people state their age. When the day of the month on the second date is earlier than the birth day, a month is “borrowed”, and the number of days is counted using the actual length of the preceding month, so February, 30-day and 31-day months are all handled correctly.
Totals in months, weeks and days are calculated from the real number of days between the dates, including leap days. All dates are treated as calendar dates without time zones, so the result does not shift depending on where you are.
Birthdays on 29 February
People born on 29 February have a calendar birthday only in leap years. In common years, this calculator treats their birthday as 28 February when working out the next birthday and whether a year has been completed. Legal conventions differ between countries — some use 1 March — so check the rule that applies if the exact date matters legally.
Common uses
Checking eligibility for school entry, sports age groups, retirement and pension rules, visa and scholarship age limits, and age-restricted services; planning milestone birthdays; and filling in forms that ask for age in years and months.
Limitations to keep in mind
- The result counts calendar days and does not consider the time of birth or time zones.
- Dates are based on the Gregorian calendar. Dates before its adoption in a given country may not match historical records.
- For legal purposes, confirm how the relevant authority treats birthdays on 29 February.
How your data is handled
Dates of birth are personal data. This calculator processes them only in your browser; they are not sent to a server or stored.
Frequently asked questions
How many days old am I?
The “Total days” figure shows the exact number of days from your date of birth to the chosen date, counting leap years.
Can I calculate an age in the future?
Yes. Set the second date to any future date to see the age someone will be on that day.
Why does my age in months not equal years × 12?
It does for complete years. The total months figure also includes the extra complete months since the last birthday, while remaining days are not counted as a month.