How do I calculate my exact age from my date of birth?

CDC/NCHS describes age as age at last birthday, often calculated from a person's date of birth and a reference date. This calculator follows that same calendar-based model and then shows the remaining months and days.

Can I check how old I was or will be on a different date?

Yes. Change the second date field to any past or future day to see the age on that specific date.

Why does February 29 affect age calculations?

NIST explains that leap years have 366 days and that century years are leap years only when divisible by 400. Because February 29 does not appear every year, calendar-based age calculations need a consistent comparison point in non-leap years.

Can I calculate a child's age in months?

Yes. CDC child and teen BMI tools support age by years and months as well as date of birth and date of measurement. This calculator can help when you need a month-level age before entering it elsewhere.

Why do some forms ask for date of birth instead of approximate age?

Exact age can change depending on the reference date, while date of birth stays stable. The U.S. Census Bureau notes that age and date-of-birth data are used to plan and fund programs for different age groups, which is one reason official workflows often start with birth date.

Does this tool show completed years or decimal age?

It shows completed calendar years first, then the remaining months and days. That is closer to the official age-at-last-birthday model than a decimal-style age.

Can I use this age calculator for a future date?

Yes. Change the reference date to a future day to check how old someone will be on that date and how close the next birthday is. This is useful when age-based rules depend on a specific future date.

Does this tool also show total days lived?

Yes. The result includes total days, weeks, and months in addition to the standard years, months, and days breakdown.

Is my birth date stored anywhere?

The calculation runs in the browser. If you use the copy-link action, the selected dates are added to the URL so the result can be reopened or shared.

Age Calculator

Find exact age from a date of birth in years, months, and days. Use it to answer how old you are now, age on another date, total days lived, and your next birthday.

Enter the dates

Enter a date of birth and, if needed, choose a different reference date. Use it to check how old you are now, on a past date, or on a future date.

Date of birth

Use a full calendar date for the most accurate result. The picker follows your device's regional date format.

Calculate age on

Leave this on today for a current age, or pick another day to compare. Displayed dates adapt to the visitor's locale.

Calculations stay in your browser. If you copy the link, the selected dates are included in the URL.

Results refresh in real time as either date changes, so there is no submit step or page reload.

Leave this on today for a current age, or pick another day to compare. Displayed dates adapt to the visitor's locale.

Age result

Use the exact age, total time lived, and next birthday details below.

Add a birth date to begin

The calculator will show the exact age, total days lived, and the next birthday as soon as a valid date is entered.

How this age calculator works

CDC/NCHS describes age as age at last birthday, or completed years counted from a date of birth to a reference date. This calculator follows that same calendar-date model, then expands the result into years, months, days, total time lived, and next-birthday timing.

1. Add the birth date

Choose the date of birth to set the starting point for the calculation.

2. Keep today or pick another reference date

Use today's date for current age, or switch the second field to calculate age on a past or future day.

3. Read the calendar breakdown

See completed years, the remaining months and days, total days lived, and the next birthday in one result block.

Why exact age matters

CDC/NCHS defines age as age at last birthday, which means completed years measured from a birth date to a reference date.

NIST notes that leap years have 366 days, and century years are leap years only when divisible by 400. That is why February 29 birthdays need calendar-aware handling.

CDC child and teen BMI tools support age by years and months or by date of birth and date of measurement, so exact age in months can matter in real pediatric workflows.

The U.S. Census Bureau says age and date-of-birth data help communities plan services for children, working-age adults, and older adults.

References and public sources

These public references support the page's calendar-based age model, leap-year handling, and why exact age can matter in real workflows.

CDC / NCHS - Age

Defines age as age at last birthday, which supports calendar-based age calculation from a date of birth to a reference date.

NIST - Leap year and leap second

Explains leap-year rules and why February 29 birthdays need calendar-aware handling in non-leap years.

U.S. Census Bureau - Why We Ask Questions About Age and Date of Birth

Shows why exact age and date-of-birth data are used in real planning and reporting workflows beyond casual curiosity.

Age calculator FAQ

How do I calculate my exact age from my date of birth?: CDC/NCHS describes age as age at last birthday, often calculated from a person's date of birth and a reference date. This calculator follows that same calendar-based model and then shows the remaining months and days.
Can I check how old I was or will be on a different date?: Yes. Change the second date field to any past or future day to see the age on that specific date.
Why does February 29 affect age calculations?: NIST explains that leap years have 366 days and that century years are leap years only when divisible by 400. Because February 29 does not appear every year, calendar-based age calculations need a consistent comparison point in non-leap years.
Can I calculate a child's age in months?: Yes. CDC child and teen BMI tools support age by years and months as well as date of birth and date of measurement. This calculator can help when you need a month-level age before entering it elsewhere.
Why do some forms ask for date of birth instead of approximate age?: Exact age can change depending on the reference date, while date of birth stays stable. The U.S. Census Bureau notes that age and date-of-birth data are used to plan and fund programs for different age groups, which is one reason official workflows often start with birth date.
Does this tool show completed years or decimal age?: It shows completed calendar years first, then the remaining months and days. That is closer to the official age-at-last-birthday model than a decimal-style age.
Can I use this age calculator for a future date?: Yes. Change the reference date to a future day to check how old someone will be on that date and how close the next birthday is. This is useful when age-based rules depend on a specific future date.
Does this tool also show total days lived?: Yes. The result includes total days, weeks, and months in addition to the standard years, months, and days breakdown.
Is my birth date stored anywhere?: The calculation runs in the browser. If you use the copy-link action, the selected dates are added to the URL so the result can be reopened or shared.

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