About this tool
Enter a date of birth and get the exact age in years, months and days, alongside the total number of days lived and a countdown to the next birthday. Leap years and varying month lengths are handled correctly.
Calendar age arithmetic is messier than it looks: subtracting dates must borrow across months of different lengths and account for February 29. This calculator walks the calendar properly instead of dividing day counts by 365, so results match how ages are legally and conventionally counted.
How to use it
- Pick the date of birth.
- Optionally change the “as of” date (defaults to today).
- Read the exact age breakdown and next-birthday countdown.
Frequently asked questions
How is age in months calculated?
By calendar months, not 30-day blocks: from 31 January to 1 March is 1 month and 1 day, since months differ in length.
What about people born on February 29?
In non-leap years, the birthday is conventionally observed on 28 February or 1 March depending on jurisdiction; this tool counts the next actual occurrence of the date or 1 March fallback.
Why does total days not equal years × 365?
Leap years add a day roughly every four years, so 30 years is about 10,957 days rather than 10,950.