Age Calculator
Calculate your exact age from your date of birth instantly. Our age calculator by date of birth shows your age in years, months, and days — plus total weeks, total days, and your next birthday countdown.
Age Calculator
Calculate exact age from date of birth — years, months, days and more
How to Calculate Age from Date of Birth
To calculate age, you subtract the date of birth from the current date (or any reference date). The calculation must handle variable month lengths — months have 28, 29, 30, or 31 days — and leap years, which add a day to February every four years. Our age calculator by date of birth handles all of this automatically.
The result breaks down as: whole years completed → remaining whole months → remaining days. For example, a person born on March 15, 1990, on December 1, 2025, would be 35 years, 8 months, 16 days old. The total in days would be approximately 13,044 days.
How to Use This Age Calculator
- 1Enter your date of birth in the "Date of Birth" field.
- 2The "Age As Of Date" defaults to today. Change it to calculate age at any point in time.
- 3Click "Calculate My Age" to see the result.
- 4The headline result shows years, months, and days.
- 5The detail row shows total days, total weeks, total months, and total years.
- 6A birthday callout shows exactly when the next birthday falls and how many days away it is.
Common Uses for an Age Calculator
Frequently Asked Questions
How do I calculate my exact age?
Enter your date of birth and the "as of" date (today by default) in the calculator above, then click "Calculate My Age." The tool returns your exact age in years, months, and days, plus the total in days, weeks, and months.
How is age calculated by date of birth?
Age is calculated by subtracting the birth date from the reference date. The result is broken down into years, then remaining months, then remaining days — accounting for variable month lengths and leap years for complete accuracy.
Can I calculate age as of a future or past date?
Yes. Change the "Age As Of Date" field to any date — past or future. This lets you calculate how old someone was on a specific historical date, or how old they will be on a future birthday.
How do I calculate age in total days?
The calculator automatically shows your total age in days, weeks, and months. The total days figure is precise, counting every actual calendar day from your birth date to the reference date, including all leap year days.
Why might my age calculation show a different result than expected?
Age calculations can differ by one day depending on whether you count the birth date itself. Our calculator measures the gap from the birth date to the reference date — so on the actual birthday, the years counter increments and the days remainder resets to zero.