How old are you, exactly? “28 years old” hides whether your 29th birthday is next week or eleven months away. This free age calculator turns any date of birth into a precise age in years, months, and days, handling leap years and uneven months correctly — plus bonus totals like days lived and a countdown to your next birthday.
Beyond curiosity, exact age matters for real paperwork: school admissions, sports age-group eligibility, retirement planning, insurance quotes, and legal age thresholds all depend on precise dates. Getting it right by hand is fiddly (try subtracting across a leap-year February); the calculator does it flawlessly.
Everything runs locally in your browser — your birth date is never sent anywhere, which matters for a piece of personal data like this.
How to use the Age Calculator
- Enter the date of birth using the date picker (or type YYYY-MM-DD).
- Click Calculate age to see years, months, and days instantly.
- Scroll the results for total days, weeks, hours lived and days until the next birthday.
- Reuse it for any date — children, parents, or historical figures.
Tips for accurate results
- For official documents, always double-check against the birth certificate — not the calculator.
- Leap-day babies (Feb 29): most systems treat Mar 1 as the birthday in non-leap years.
- Age ‘in months’ is handy for pediatric milestones; this tool shows both.
- Your date of birth never leaves your device — safe to use on shared computers too.
How exact age is calculated
The algorithm borrows like column subtraction: if today's day-of-month is smaller than the birth day, it borrows the previous month's length; if the month goes negative, it borrows 12 months from the year. Leap years are handled automatically because the calculation uses real calendar dates, not 365-day approximations.
Frequently asked questions
How is exact age calculated?
By comparing year, month, and day components separately and borrowing (like subtraction) when the current day or month is smaller than the birth day/month — correctly handling leap years.
What day of the week was I born?
This calculator focuses on age totals; your weekday of birth needs a day-of-week tool. (Fun fact: the weekday repeats on a 400-year Gregorian cycle.)
Is my birth date stored or sent anywhere?
No. The calculation happens entirely in your browser with JavaScript — nothing is uploaded or logged.
Can I calculate age at a past or future date?
This tool calculates age as of today. For age on a specific date (e.g., ‘how old was I on Jan 1, 2020?’), subtract manually or use a date-duration calculator.