🎂 Age Calculator
Calculate exact age in years, months, and days from a birth date. Find days until next birthday, total days lived, and date-to-date intervals.
About this tool
The Age Calculator turns a birth date into a precise age: years, months, and days, computed the calendar way (so a baby born on March 31 reads as 1 month, not 1.03 months, even in a 30-day April). Beyond the headline number you get the total days, weeks, and hours you have been alive, an estimate of your lifetime heartbeats (at a resting 72 bpm), the day of the week you were born, your day-of-year number, and your Western and Chinese zodiac signs.
The Next birthday panel shows how many days remain until your next birthday along with a progress bar that tracks where you are in the current birthday-to-birthday cycle — handy for planning and for the perennial "how many days until my birthday?" question. Set the Age as of date to any day in the past or future to find out your age on that exact date.
Examples:
- Born
1995-03-15, as of2026-07-05→ 31 years, 3 months, 20 days (born on a Wednesday, day 74 of 365, Pisces, Pig). - Born
2000-02-29(leap day), as of2026-02-28→ 25 years, 11 months, 30 days; the next birthday is counted as February 28 in non-leap years.
FAQ
How is the age calculated? ›
The tool compares the birth date with the reference date component by component — years, then months, then days — borrowing from the next larger unit when needed, exactly the way you would do it by hand. This is calendar-accurate: it accounts for months of different lengths and for leap years, so it never drifts the way dividing total milliseconds by 365.25 does.
What happens for a February 29 birthday? ›
In common (non-leap) years the next birthday is treated as February 28, the last day of February. The age math itself is still exact: someone born on Feb 29, 2000 is, on Feb 28, 2024, 23 years, 11 months, and 30 days old, and turns 24 on Feb 29, 2024.
Can I find my age on a future or past date? ›
Yes. Change the "Age as of" field to any date — past, present, or future — and the tool recomputes everything for that reference date. This is useful for "how old will I be on this date" questions, or for checking how old someone was on a historical date.
How are the heartbeats estimate calculated? ›
It multiplies your total hours alive by 60 minutes and a resting heart rate of 72 beats per minute. It is a rough, curiosity-only figure: your real resting and active heart rate varies, so treat it as an order-of-magnitude estimate, not a medical measurement.
Does the day-of-week calculation use the right calendar? ›
Yes. The JavaScript Date object handles the Gregorian calendar including the switch from the Julian calendar, so the day of the week is correct for any date in the supported range of the date input (year 1 onwards in most browsers).
How is this different from the Date Calculator? ›
The Age Calculator specializes in computing exact age from a birth date, with birthday milestones, days until next birthday, and fun statistics like total heartbeats. For general date math — adding or subtracting time from any date, difference between any two dates, counting business days, or inspecting a date's ISO week and quarter — use the <a href="/date-calculator">Date Calculator</a>.