About this tool
Figuring out someone's exact age — or the precise gap between two dates — gets fiddly once you account for varying month lengths and leap years. This calculator takes a date of birth and a reference date and returns the exact age broken down into years, months, and days, along with the total day count and a countdown to the next birthday.
How to use it
- 1Enter the date of birth.
- 2Enter the date you want to calculate age as of (defaults to today).
- 3Read the exact age in years, months, and days, along with total days lived and days until the next birthday.
Common mistakes to avoid
- Manually subtracting years without adjusting for whether the birthday has already occurred this year.
- Forgetting leap years when counting total days between two dates.
- Assuming every month has the same number of days when calculating the months/days breakdown.
Use cases
- Confirming exact age for a legal, medical, or eligibility requirement.
- Calculating age as of a specific past or future date, not just today.
- Finding out how many days remain until an upcoming birthday.
- Calculating the precise duration between any two events, like an anniversary or project start date.
Frequently asked questions
Does this account for leap years?
Yes. The calculation uses native JavaScript Date arithmetic, which correctly accounts for leap years and variable month lengths.
Can I calculate age as of a date other than today?
Yes. Change the "Age as of" field to any date to see the exact age at that point in time, whether in the past or future.
Is my birth date stored anywhere?
No. All calculations happen locally in your browser and are not saved or transmitted.