How to use the age calculator
Enter a date of birth. The calculator fills in today's date, but you can change it to find someone's age on any date, for example on the day an application closes. You get the exact age in years, months and days, plus the total in months, weeks, days and hours, the day of the week the person was born and the next birthday.
How age is calculated
Age = whole years + whole months + remaining days
The calculator counts whole years from the birthday, then whole calendar months, then the days left over. When a month is shorter than the birth date (for example, born on the 31st), it uses the last day of that month. Total days include every leap day.
Worked example
Born 15 May 1990, age on 30 October 2026:
15 May 1990 to 15 May 2026 = 36 years. 15 May to 15 October = 5 months. 15 October to 30 October = 15 days. Age: 36 years, 5 months, 15 days, which is 13,317 days.
Age in different countries
This calculator uses the international way of counting age, where you're 0 at birth and add a year on each birthday. South Korea officially moved to this system in 2023. Some traditions in East Asia still count a newborn as 1 year old.
To count the days between any two dates, use the date calculator.
Frequently asked questions
How old will I be on a certain date?
Change the "Age on this date" box to that date. The result updates instantly.
What if I was born on 29 February?
In years without a leap day, the calculator treats 28 February as your birthday. Legal rules differ: some countries use 1 March.
Why can this differ from Excel by a day or two?
When the birth date is late in a month (the 29th to 31st), people count months differently. This calculator counts whole months first and uses the last day of a shorter month, the same method as timeanddate.com. Excel's DATEDIF counts the leftover days differently, so its "months and days" can differ slightly. The total number of days is always the same.
Are leap years included?
Yes. The total number of days counts every 29 February between the two dates.
Formulas checked 29 October 2026. How we test our calculators. Check important deadlines, hours and pay against the official rules and records that apply to you.