Age Calculator — Calculate Age from Date of Birth
Calculate exact age in years, months, and days from a birthdate. Also find age on a specific date and number of days since birth.
By SwiftCalcTools Editorial Team · Formula verified
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How to Use Age Calculator
- 1Enter the required values in the input fields above.
- 2Click the Calculate button or results update instantly as you type.
- 3View your results in the output panel below the inputs.
- 4Adjust any values to recalculate instantly.
Frequently Asked Questions
Age is calculated by subtracting the birth date from the reference date in years, months, and days. When the day of the reference date is less than the birth day, we borrow from the previous month. When the month is less than the birth month, we borrow a year and add 12 months.
Total months = (years × 12) + remaining months. For example, 25 years and 3 months = 303 months total. This is how many calendar months have passed since birth, which is different from the years/months/days breakdown shown.
Chronological age is the time elapsed since birth. Biological age reflects the state of your cells and organs — it can be younger or older than your chronological age depending on genetics, lifestyle, diet, and exercise habits. Biological age is measured through biomarkers like telomere length and epigenetic clocks.