Age Calculator in Months and Days

Calculating an exact age by hand is fiddly because months have different lengths and leap years add an extra day. This age calculator gives the precise age in years, months and days, plus totals in months, weeks, days and hours, the day of the week someone was born, and how many days remain until their next birthday.

Common uses

• Check eligibility for school entry, sports categories, visas, pensions or competitions on a cut-off date.
• Fill in forms that ask for age in years and months.
• Find out how many days old you are for a fun milestone like 10,000 days.
• Calculate the age of a company, building, pet or relationship.

Tips for best results

• Always use the cut-off date stated by the organisation, not today's date.
• Ages are calculated from calendar dates, so time zones do not matter.
• For age in another calendar system, convert the date first.
• Use the Date Difference Calculator for working days between dates.

How age is calculated

The calculator counts full years first, then full months, then remaining days, borrowing days from the previous month when needed – the same method used on official forms. For example, from 31 January to 1 March is 1 month and 1 day in a non-leap year. Totals such as days and weeks are exact counts of calendar days between the two dates.

Age conventions around the world

Most countries use the international age system shown here, where you are 0 at birth and gain a year on each birthday. South Korea officially switched to this system in 2023, replacing its traditional counting; parts of East Asia still use traditional reckoning informally. When forms ask for age, use the international system unless told otherwise.