Enter a birth date and an "as of" date; the exact age and total days lived update as you change either field.
Change either date at any time and the age and total-days figures recalculate immediately - there is no separate "calculate" button to press.
If the birth date is missing or falls after the "as of" date, the tool shows a prompt to fix it instead of a wrong or negative result.
For a field-by-field walkthrough with worked examples, see the age calculator step-by-step guide.
Age Calculator
Work out an exact age in years, months, and days from a birth date.
Key features
- The "as of" field defaults to today's date, but you can pick any date to check age as of that day.
- The birth date and the "as of" date stay in the browser - the age is worked out on this device, with no upload and no account.
Common uses
Use it to check an exact age for a form, an eligibility cutoff, or just out of curiosity.
Not sure this is the right fit for what you need right now? See when to use the age calculator.
Good to know
Does not provide medical or financial advice - results are general estimates only.
How the exact age and total days lived are calculated
Age Calculator builds the years/months/days line from the two calendar dates you enter, not from a fixed 30-day-month shortcut. It first subtracts the year, month, and day components directly. When that leaves a negative day count, it re-adds the actual number of days in the previous calendar month - 28, 29, 30, or 31, whichever that specific month really has - instead of always subtracting a flat 30. That ties the day figure to the real calendar rather than an approximation. For example, a birth date of January 15 checked against March 1 of the same year comes back as 1 month and 14 days, not a rounded-off "1 month and a bit" - the 14 days come from February contributing its own real length to the borrow.
Alongside the years/months/days line, Age Calculator also reports total days lived: the exact number of days between the two dates, rounded to the nearest whole day and shown with thousands separators once the count climbs into the thousands - 13,394 rather than 13394, for example. Both figures come from the same pair of date fields and update together, so you always see the breakdown and the day total side by side. A birth date of January 1, 1990 checked against September 3, 2026, for example, comes back with a total of 13,394 days lived - a scale that's easy to lose track of from the years/months/days figure alone.
Before you change anything, the birth-date field opens pre-filled with January 1, 2000, and the as-of field opens pre-filled with today's date - both editable right away rather than starting blank.
Frequently Asked Questions
What does Age Calculator do?
Work out an exact age in years, months, and days from a birth date.
When should I reach for age calculator?
Use it to check an exact age for a form, an eligibility cutoff, or just out of curiosity.
What complementary tools work well alongside age calculator?
Defaults to today's date for the "as of" field, but you can pick any date to check age as of that day.
Can I type a date directly into the birth-date or as-of field?
Not as free text. Both fields are native browser date pickers, so every value you set is already a real calendar date before Age Calculator does any math on it - there is no way to enter a half-typed or malformed date.
What happens if I set the birth date and the as-of date to the same day?
Age Calculator reports 0 years, 0 months, 0 days, and 0 total days lived, confirming the two dates match rather than showing an error or a blank result.
What happens if the calculation hits an unexpected error?
The calculation runs inside a safety check. If anything ever goes wrong, Age Calculator shows a plain "Could not start the tool" message with the specific error attached, instead of leaving the page blank or frozen.
Does the total-days number always show comma separators, like 13,394?
It uses your browser's locale-aware number formatting to add those separators. If a browser somehow lacks that formatting support, Age Calculator falls back to a plain rounded number instead of breaking - you still get a usable total, just without the commas.