What this calculator does
Age calculator works out exact age in years, months and days, plus the next birthday. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaYears = whole years between the dates; remaining months and days are counted forward from the last birthday
The inputs explained
| Field | What to enter |
|---|---|
| Date of birth | A calendar date. |
| Age at this date | A calendar date. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Examples across different dates
The same calculation at a range of dates, with every other input held at its starting value. These are generated relative to the day the page was built.
Examples across different dates
| Date of birth | Age | In total days | In weeks |
|---|---|---|---|
| 2021-08-04 | 5 years, 0 months, 0 days | 1,826 | 261 |
| 2011-08-04 | 15 years, 0 months, 0 days | 5,479 | 783 |
| 2001-08-04 | 25 years, 0 months, 0 days | 9,131 | 1,304 |
| 1991-08-04 | 35 years, 0 months, 0 days | 12,784 | 1,826 |
| 1981-08-04 | 45 years, 0 months, 0 days | 16,436 | 2,348 |
| 1966-08-04 | 60 years, 0 months, 0 days | 21,915 | 3,131 |