Age Calculator
Calculate your age
What Is This Tool?
The Age Calculator computes an exact age in years, months, and days from a birth date, along with total days lived and a countdown to the next birthday. You can also calculate age as of a specific past or future date instead of today.
How to Use
Select a birth date.
Optionally choose an "as of" date; leave it blank to use today's date.
Click Calculate to see exact age, total days lived, and the days until the next birthday.
Features
- Calendar-aware years/months/days breakdown
- Total number of days lived
- Days remaining until the next birthday
- Optional "as of" date for calculating age at any point in time
- Validates that the birth date is not in the future
- 100% client-side — nothing leaves your browser
Examples
Birth Date: a date roughly 28 years ago
Output: Exact Age: 28 years, X months, Y days · Total Days Lived: ~10,200 · Days Until Next Birthday: varies
Common Use Cases
- Calculating exact age for forms, eligibility checks, or legal documents
- Finding out how many days old you (or someone else) are
- Counting down the days until an upcoming birthday
- Calculating someone's age as of a specific past event date
Frequently Asked Questions
Can I calculate age as of a date other than today?
Yes, fill in the optional "As Of Date" field. If you leave it blank, the calculator uses today's date automatically.
What happens if I pick a future birth date?
The tool validates that the birth date is not after the "as of" date and shows an error if it is, since a future birth date can't produce a valid age.
How is the next-birthday countdown calculated?
It finds the next occurrence of your birth month and day on or after the "as of" date, rolling over to next year if this year's birthday has already passed, and reports the number of days until then.
Is the years/months/days breakdown calendar-accurate?
Yes, it walks actual calendar months (which vary in length) rather than assuming a fixed 30-day month, and correctly accounts for leap years.
Is my birth date sent anywhere?
No. All calculations happen locally in JavaScript in your browser. Nothing is uploaded or logged.
What if someone was born on February 29th?
In non-leap years, the next-birthday calculation will land on March 1st for that person's countdown, since February 29th does not exist in those years.