Age Calculator
Find your exact age in years, months, and days based on your birth date and any target date — past, present, or future.
Your age breakdown will appear here
Enter a date of birth and a target date, then click calculate to see the breakdown.
Quick Answer
An age calculator finds your exact age in years, months, and days by calculating the difference between your birth date and today's date (or any chosen date).
How It Works: Formula & Variables
Age = Target Date − Birth Date (broken into years, months, and days)
- Birth Date
- The date you were born.
- Target Date
- The date you want your age calculated as of — defaults to today, but can be any past or future date.
The calculation accounts for varying month lengths and leap years, rather than estimating with a flat 365-day year.
Worked Examples
Example 1: Standard birth date
Someone born on March 15, 1990, calculated as of June 21, 2026, is 36 years, 3 months, 6 days old.
Example 2: Leap day birthday
Someone born on February 29, 2000 (leap day), calculated as of June 21, 2026, is 26 years, 3 months, 23 days old — their birthday is observed as Feb 28 in non-leap years.
Key Concepts
Leap years: A leap year adds a day every 4 years to keep the calendar aligned with Earth's orbit, with exceptions for century years not divisible by 400.
Age in years alone hides precision: Saying someone is "36 years old" hides how many months and days have passed since their last birthday.
Cultural age differences: Some cultures count age differently — for example, traditional Korean age adds a year at birth rather than starting at zero.
Common Mistakes
Forgetting leap years: Manually counting days between dates without accounting for leap years can throw off the result by a day or more.
Assuming every month has 30 days: Months range from 28 to 31 days, so a flat 30-day assumption produces inaccurate month and day counts.
Off-by-one errors: Forgetting that a birthday hasn't occurred yet this year can lead to claiming one year older than is accurate.
Frequently Asked Questions
Age is calculated by finding the full number of years, then months, then days between your birth date and the target date, accounting for the actual number of days in each month and leap years — not a flat 365-day average.
Someone born on February 29 typically observes their birthday on February 28 in years that aren't leap years, since that date doesn't exist.
Yes — change the 'calculate age as of' field to any date, past or future, to see age at that point in time.
Total days lived adds up quickly — a 30-year-old has lived roughly 10,950+ days, which is why the total looks large compared to age in years.