About this tool
This calculator works out the exact time elapsed between a birth date and any reference date (today, by default) using real calendar arithmetic — so leap years and varying month lengths are handled correctly. Everything runs client-side in your browser.
How to use the Age Calculator
- Enter the date of birth using the date picker.
- Leave "Age as of" set to today, or change it to see the age on a past or future date.
- Read the breakdown — years/months/days, total days and weeks lived, and days until the next birthday.
Common use cases
- Checking eligibility for age-restricted forms, school admissions, or exams
- Working out someone's exact age for legal or medical documentation
- Finding a baby's age in weeks or months for milestone tracking
- Counting down the days to a birthday or a future eligibility date (like retirement age)
Worked example
Someone born on March 14, 1994, checking their age on this date in 2026 would show 32 years, roughly 5-6 months, and a handful of days, depending on how many days have passed since their last birthday this year — the tool computes this precisely rather than estimating. Set "Age as of" to a future date, like a retirement eligibility date, and the same logic runs forward: you'll see exactly how many years and months remain, which is useful for pension or benefits planning where an exact date matters more than a rounded year count.
Things to watch out for
Age "in years" always means completed years — someone who is 29 years, 11 months, and 20 days old is still 29, not 30, until the exact anniversary date. The total-days and total-weeks figures are calendar-exact counts, not rounded estimates, so they're useful for anything requiring precision (like calculating a child's exact age in days for a medical dosage chart, which should always be confirmed with a professional rather than a web tool). If the birth date is set after the "age as of" date, the result isn't meaningful — the calculator assumes the reference date comes after the birth date.
If you've ever gotten a slightly different months/days breakdown from two different age calculators, see Why Age Calculators Give Different Answers.
How the years, months and days are worked out
The calculator counts whole months first, then the days left over. This is the same rule Java's Period.between uses:
- Count the complete months from the birth date to the "as of" date. A month is complete when the "as of" day reaches the birth day. If the birth day doesn't exist in that month (the 31st in September, say), the month's last day counts instead.
- Split those months into years (every 12 months) and the remaining months.
- Count the days from the last completed month back to the "as of" date.
For example, someone born on June 15, 1990 is 36 years, 3 months and 15 days old on September 30, 2026: 2026 − 1990 = 36 years, September − June = 3 months, and 30 − 15 = 15 days, with no borrowing needed. Someone born on March 14, 1994 is 32 years, 6 months and 16 days old on the same date. Someone born on August 31, 1990 is 36 years, 1 month and 17 days old on October 17, 2026: the last completed month ends on September 30, because September has no 31st, and 17 days have passed since then.
Turning the result into months or weeks
To express an age in months only, multiply the years by 12 and add the months: 36 years and 3 months is 36 × 12 + 3 = 435 months. Leftover days are simply dropped, because a month is only counted once it is complete. The weeks figure works the same way: the total number of days divided by 7, rounded down. That makes both numbers "completed" counts, just like the years figure.
Birthdays on February 29
A leap-day birthday only occurs in leap years. In the Gregorian calendar a year is a leap year if it is divisible by 4, except century years, which must also be divisible by 400, so 2000 was a leap year and 2100 will not be. In other years this calculator treats the day after February 28, which is March 1, as the next birthday when it counts the days remaining. Someone born on February 29, 2008 shows as 17 years, 11 months and 30 days old on February 28, 2026. If you celebrate on February 28 instead, subtract one day from the countdown. Where an exact legal age matters, such as a licence or contract, check the rule the relevant authority uses for leap-day births rather than relying on any calculator.
For the reasons different sites can disagree by a day or two, see how age calculators work. To count forward from a date rather than back, use the Date Calculator.
Frequently asked questions
Yes. The calculator uses actual calendar dates, so leap years are handled automatically and don't throw off the year, month, or day count.
Yes — set the "Age as of" field to any date, past or future, to see what someone's age was or will be on that date.
Different tools calculate months and days differently since calendar months vary in length (28-31 days). This calculator counts full elapsed calendar months and then the remaining days, which matches how age is stated on most official documents.
No. The calculation runs entirely in your browser using JavaScript — nothing is uploaded or saved.
Multiply your completed years by 12 and add the extra completed months shown by the calculator. For example, 32 years and 6 months is 32 × 12 + 6 = 390 months. Any leftover days are not counted, because a month only counts once it has fully passed.
They gain a year when the date moves past February 28. This calculator shows a February 29, 2008 birth as 17 years, 11 months and 30 days on February 28, 2026, and counts March 1 as the next birthday. Legal rules for leap-day births can differ, so check them where it matters.