How Your Exact Age is Calculated
Knowing your exact age in years, months, and days is often necessary for legal forms, medical records, passports, and life insurance applications. Our Date of Birth Calculator removes the complexity of mental date math, instantly accounting for leap years and months of differing lengths.
Need to find the difference between two arbitrary dates rather than a birthdate? Check out our standard Date Difference Calculator.
Chronological vs. Biological Age
- Chronological Age: The exact amount of time that has passed since your date of birth. This is what this calculator computes and is the standard metric used worldwide.
- Biological Age: A concept that measures how your body is aging internally compared to your chronological age. This is influenced by genetics, lifestyle, diet, and stress.
The Logic Behind Date Math
Calculating the exact difference between a birth date and today requires "borrowing" from months and years, similar to long subtraction:
- Subtract the birth Day from the current Day. If the result is negative, we "borrow" a month, adding the number of days from the previous month to the current day.
- Subtract the birth Month from the current Month. If negative, we "borrow" a year, adding 12 months to the current month.
- Subtract the birth Year from the current Year.