Age Calculator
Calculate age
Calculate age Runs locally in your browser
Your date of birth, in YYYY-MM-DD format.
About the
The Age Calculator gives your exact age in years, months and days, plus the total number of days lived and a countdown to the next birthday. The reason it is not simply a subtraction of two years is that months have different lengths and birthdays fall on different days, so a naive calculation is wrong by a day or a month for most of the year. It also answers the question that forms and legal documents actually ask: your age on a specific date, which is not the same as your age today and cannot be produced by subtracting years alone.
Where people use the
- Filling in an age field on a form that wants years and months.
- Checking whether someone meets an age requirement on a given date.
- Working out how many days until a birthday for planning.
- Converting a date of birth into total days for a data migration.
How to use the
- 1
Enter the date of birth
Use the calendar field rather than typing, which avoids ambiguity between day-first and month-first formats.
- 2
Optionally set a reference date
Leaving it empty uses today. Setting it answers questions such as age at a future exam date or on a historical date.
- 3
Read the breakdown
Years, months and days are shown separately, with the total days and weeks below. The year and month figures are what most forms want.
- 4
Check the next birthday
The countdown is useful for planning, and it also reveals the leap-day case: a 29 February birthday falls on 1 March in non-leap years in most jurisdictions.
Tips and best practices
- For a form, use the years figure only; adding months invites disagreement with the reviewer.
- When an age requirement applies on a specific date, set that date as the reference rather than using today.
- If two sources disagree by exactly one day, check whether one of them counts elapsed time and the other counts inclusive days.
Frequently asked questions
Why is my age not just this year minus my birth year?
Because that only counts completed years if your birthday has already passed this year. If it has not, you are one year younger than the subtraction suggests. The calculator compares month and day as well as year.
How are leap days handled?
For someone born on 29 February, the birthday exists only every fourth year. Most legal systems treat 1 March as the anniversary in common years, some use 28 February. The countdown here uses 1 March, and the year count is unaffected either way.
What is the difference between chronological and corrected age?
For a premature baby, chronological age counts from birth while corrected age counts from the expected due date. Paediatric growth charts use corrected age until about two years. This tool reports chronological age.
Does the first day count as day one?
This calculator counts elapsed time, so the day of birth is day zero. Some East Asian traditions count the birth day as day one, which makes everyone a year older by that convention. Both are self-consistent; just be clear which one a form expects.
Why does the total day count differ from what I calculated?
Because of leap years. Every four years adds a day, with century years skipped unless divisible by 400. The total here counts actual calendar days between the two dates rather than multiplying years by 365.
Can I use this for legal or medical purposes?
As a cross-check, yes. For anything with a deadline attached, calculate from the statutes that apply, which sometimes define age differently for specific purposes, and confirm the result on the official form.