Completed years
A year is completed when the birthday is reached. Before that birthday, the previous completed-year age remains correct.
Date and time calculator
All calculatorsAge Calculator
Calculate exact age from a date of birth in years, months and days. You can also see total days lived, full weeks, the next birthday and how the result was calculated.
Interactive tool
Calculate exact age
Calendar based
Exact ageEnter a date of birth
Choose a date of birth and select Calculate age.
0Years
0Months
0Days
Total days—
Full weeks—
Born on—
Next birthday—
Direct answer
How is age calculated?
Age is calculated by comparing a date of birth with a selected target date. First count the completed years. Then count the completed months after the most recent birthday, followed by the remaining days.
A simple subtraction of the two year numbers is not always enough. If the birthday has not happened yet in the target year, the completed age is one year lower than the basic year difference.
The age formula
Current year minus birth year, with a birthday adjustment
The basic age formula starts by subtracting the birth year from the target year:
Basic age formulaAge = Target year − Birth year
After finding the year difference, check the birth month and birth day. If the birthday has not yet occurred on the selected date, subtract one year.
The calculator goes further by finding completed months and remaining days. This gives an exact calendar age rather than only a whole-year result.
Birthday check
Has the birthday happened?
Birthday has passed
Use the full difference between the two years.
Birthday has not passed
Subtract one year from the basic year difference.
Worked example
Age calculation step by step
Suppose a person was born on 10 June 2000 and you want to calculate their age on 24 June 2026.
- 1Find the completed years
From 10 June 2000 to 10 June 2026 is 26 completed years.
- 2Count completed months
The selected date is still within the same calendar month, so no additional completed month is added.
- 3Count the remaining days
From 10 June to 24 June is 14 days.
Exact age on 24 June 202626 years and 14 days
Understanding the result
Years, months and days measure different completed periods
Exact age is not created by dividing total days by 365. Calendar years and months have different lengths, so each completed period must be counted using real calendar dates.
Completed months
Months are counted after the latest completed birthday. Their actual calendar lengths are used rather than assuming 30 days.
Remaining days
Days are counted after the last completed month. This produces the final exact calendar-age result.
Past and future dates
Calculate age on any selected date
The second input does not have to be today. You can enter a past or future target date to find a person's age on that specific date.
This can be useful when checking an age requirement, preparing a historical record, finding age on an application deadline, or determining how old someone will be on a future event date.
The target date must be the same as or later than the date of birth. A date before the birth date cannot produce a valid age.
Common uses
- School and college admission cut-off dates
- Job and examination eligibility
- Sports age categories
- Insurance and administrative forms
- Age on a historical or future date
- Personal milestones and birthday planning
Leap-year birthdays
How is a February 29 birthday handled?
A person born on February 29 has an exact calendar birthday only in leap years. In non-leap years, calendar systems and legal rules may treat the anniversary as February 28 or March 1 depending on the purpose and jurisdiction.
For the calculator's calendar arithmetic, February 29 is clamped to the final valid day of February when the selected year does not have a February 29. This keeps the years, months and days calculation consistent.
Leap yearFebruary 29Birthday date exists
Non-leap yearFebruary 28Calendar calculation date
Common mistakes
Avoid these age-calculation errors
Subtracting years only
This can make the result one year too high when the birthday has not yet happened.
Treating every month as 30 days
Calendar months contain 28, 29, 30 or 31 days, so exact age must use real dates.
Ignoring the target date
Age today may differ from age on an application deadline or another selected date.
Using total days as exact age
Dividing total days by 365 does not correctly reproduce calendar years, months and days.
Age Calculator guides
Learn more about calculating age
Use these supporting guides for exact age, future and past dates, total days, weeks, leap years, and birthday countdowns.
Supporting guideHow to Calculate Age from Date of Birth
Calculate age correctly from a date of birth by checking whether the birthday has occurred.
Read guide →Supporting guideHow to Calculate Age in Years, Months, and DaysFind exact age using completed years, months, and remaining days.
Read guide →Supporting guideAge Calculator for a Future DateCalculate how old someone will be on a selected future date.
Read guide →Supporting guideHow to Calculate Age in MonthsConvert completed years and additional calendar months into age in months.
Read guide →Supporting guideHow to Calculate Age in DaysCount the complete calendar days between a date of birth and target date.
Read guide →Supporting guideAge Difference Between Two PeopleCompare two dates of birth and calculate the age gap between them.
Read guide →Supporting guideLeap-Year Birthday Age CalculationUnderstand how February 29 birthdays are handled in non-leap years.
Read guide →Supporting guideHow Old Was I on a Certain Date?Calculate exact age on a historical date instead of today's date.
Read guide →Supporting guideHow to Calculate Age in WeeksConvert total age in days into complete weeks and remaining days.
Read guide →Supporting guideHow Many Days Until My Next Birthday?Calculate the number of calendar days remaining before the next birthday.
Read guide →How do I calculate my exact age?
Compare the date of birth with the selected target date. Count completed years first, then completed months after the most recent birthday, followed by the remaining days.
Why is age not always current year minus birth year?
The birthday may not have happened yet in the selected year. If it has not happened, subtract one year from the basic year difference.
Can I calculate age on a past date?
Yes. Enter the past date in the Age on date field. It must be the same as or later than the date of birth.
Can I calculate age on a future date?
Yes. Choose any future target date to see how old the person will be on that date.
What is completed age?
Completed age is the number of full years a person has lived. A new completed year is added only when the birthday is reached.
What does age in years, months and days mean?
It separates the exact calendar difference into completed years, completed months after the last birthday, and the remaining days.
Does the calculator use 365 days for every year?
No. It uses real calendar dates, including the different lengths of months and leap years.
How is a February 29 birthday calculated?
For calendar arithmetic, the anniversary is adjusted to the final valid day of February in a year that does not contain February 29.
Can the date of birth be after the target date?
No. The target date must be the same as or later than the date of birth.
Is this calculator suitable for official forms?
It can help with calendar calculations, but official organisations may apply their own cut-off dates, legal definitions or leap-day rules. Check the requirements of the relevant organisation.
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Use the Age CalculatorFind exact age in seconds
Return to the calculator, enter a date of birth and choose the date on which you want to calculate age.