Age Calculator – Exact Age in Years, Months & Days
Enter a birth date (and an optional “as of” date) to get exact age, days lived, and next-birthday countdown.
An exact age matters for forms, eligibility cutoffs, and milestones — not just “I’m 30.” This age calculator breaks the span from birth to a chosen day into years, months, and days, then adds total days lived and how long until the next birthday.
Calendar math respects month lengths and leap years. February 29 births use February 28 in non-leap years so age never stalls or goes negative. Everything runs in your browser; nothing is uploaded.
Need the gap between any two dates (not just birthdays)? Try the Date Difference Calculator.
How to use
- Enter the date of birth with the date picker.
- Leave “As of” blank for today, or pick another date to age someone as of that day.
- Read years, months, and days, plus total days lived and the next-birthday countdown.
- Use Reset to clear and start over.
Tips
- Dates use your local calendar day — no time-of-day or time-zone shift surprises.
- Someone born on February 29 is treated as turning a year older on February 28 in non-leap years.
- If “as of” is before the birth date, you’ll see a clear error instead of a negative age.
- Total days lived counts calendar days between the two dates (birthday = day 0).
FAQ
How is exact age calculated?
Years, months, and days are counted on the calendar: full years first, then remaining months, then remaining days. Month lengths and leap days are included automatically.
What if my birthday hasn’t happened yet this year?
Your age in years stays at last year’s birthday until the birth month and day arrive. The months and days fields show how far you are into the current year of life.
How are February 29 birthdays handled?
In leap years, February 29 is used as usual. In non-leap years, this calculator treats the birthday as February 28 for age and next-birthday countdown.
Does “as of” work for future dates?
Yes. Set “as of” to a future day to see how old someone will be then, or how many days until a future birthday relative to that date.
What is “total days lived”?
It is the number of whole calendar days from the birth date up to (but not including) the “as of” date. On your birthday itself, that count equals your age in days.
Why does next birthday show 0 days?
When the “as of” date falls on the birthday (or the February 28 stand-in for a Feb 29 birth in a non-leap year), the countdown is 0 — it’s birthday day.