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Find your precise age in years, months, and days — plus weeks lived, day of week you were born, and a countdown to your next birthday.
An age calculator is a tool that measures the exact time between two dates — usually your date of birth and today — and expresses the result in years, months, and days. It handles leap years, varying month lengths, and fractional remainders automatically, so the answer is always accurate down to the day. Most people reach for one when filling out a form, tracking a birthday milestone, or confirming eligibility for something tied to a specific age (retirement, insurance, school enrollment). This calculator also shows your total weeks, days, hours, and minutes lived, the day of the week you were born on, and a countdown to your next birthday and the next round-number milestone age. Everything runs in your browser; no dates are sent to a server.
Type or pick the year, month, and day you were born. The calendar picker enforces a valid date automatically.
It defaults to today. Change it to any later date to see what your age will be at a future milestone, or an earlier date to compute an age at a past event.
Your result updates instantly in three parts: full years, remaining months, and remaining days.
Below the main result you'll see your lifetime totals in weeks, days, hours, and minutes — useful for count-ups and personal milestones.
The 'Next birthday' card shows the exact date and weekday of your upcoming birthday and the age you'll turn. The milestone progress bar tracks how close you are to the next round-number age (18, 21, 30, 40, 50, 60, 65, 70, 75, 80, 90, 100).
age = to_date − from_date years = to.year − from.year months = to.month − from.month days = to.day − from.day if (days < 0): borrow from previous month if (months < 0): borrow from year
The age calculator takes the calendar difference between the two dates rather than a simple day count. If the day-of-month in the 'as of' date is earlier than the birth day, it borrows a month (using the number of days in the previous calendar month — which correctly handles 28/29/30/31-day months). If months then go negative, it borrows a year. This mirrors how people say an age in everyday language: a person born on March 15 becomes "X years and 0 days" exactly on March 15, not on the average day of the year.
Reference: Wikipedia — Age
| Date of birth → as of date | Age |
|---|---|
July 4, 1990 → July 4, 2025 | 35 years, 0 months, 0 days Exact birthday: years tick over, months and days are zero. |
December 31, 1999 → January 1, 2026 | 26 years, 0 months, 1 day New-year's-eve birthday: one calendar day past the 26th birthday. |
February 29, 2000 → February 28, 2025 | 24 years, 11 months, 30 days Leap-day edge case: 2025 isn't a leap year, so the 25th birthday is March 1. |
March 10, 1985 → April 20, 2026 | 41 years, 1 month, 10 days — next birthday in 324 days Countdown view: same DOB shows weeks lived (~2,144), next birthday weekday, and progress toward turning 50. |
Count days, weeks, months, and years between any two dates with business-day totals.
Check body mass index from height and weight using metric or imperial units.
Work out percentages, percentage change, and percentage of a total in seconds.
Add a tip, split the bill, and share the total evenly across a group.
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