Age calculator — your exact age and days between dates

How exact age is calculated in years, months and days

Exact age is calendar subtraction with borrowing — the same way you subtract time on a clock. The calculator subtracts your birth year, month and day from today's date. If today's day-of-month is smaller than your birth day, it borrows the length of the previous month; if the months go negative, it borrows twelve months from the years. Because months are not all the same length, the math has to respect the real calendar — leap years included — which is why a rounded "divide by 365" answer is often a day or two off.

To get your exact age:

• Open the Age Calculator and pick your date of birth.
• Read the three columns: full years, remaining months, remaining days.
• Check the summary line below: total days lived and days until your next birthday.

How old am I in days, weeks or months?

Your age in days is the count of real calendar days since you were born, leap days included. A year averages 365.25 days, so 25 years works out to roughly 9,131 days — but the exact figure depends on how many February 29ths you have lived through, which is why the Age Calculator counts actual days rather than multiplying.

Age in months is simpler: full years times 12, plus the remaining months from the breakdown — someone who is 24 years and 7 months old is 295 months old. For age in weeks, divide the days-lived total by 7, or enter your birth date and today's date into Date Difference, which shows the weeks figure directly alongside days and months. The expected result is one screen with every version of the answer — no separate lookups.

Days between two dates — inclusive vs exclusive counting

Most confusion about counting days comes down to one choice: do you count both endpoint days or not? Exclusive counting measures elapsed time — from January 1 to January 5 is 4 days, the way hotel nights or interest periods are counted. Inclusive counting adds the starting day itself — the same span becomes 5 days, which is how medication courses, rental "days" and some legal deadlines work.

The Date Difference tool uses the standard exclusive count. To use it: pick your two dates (the order does not matter), then read the result — total days, weeks, months, and a years/months/days breakdown of the span. If your task counts both the first and the last day, add 1 to the days figure. That single rule resolves nearly every "why is my count off by one?" moment.

Next-birthday countdown and milestone dates

The Age Calculator shows the days remaining until your next birthday automatically — it handles the year rollover, and on the day itself it reads 0. For any other event — a wedding, an exam, a visa deadline, the start of Ramadan — enter today's date and the event date in Date Difference and the days figure is your "how many days until" answer.

Milestone dates are a fun use of the same math: you turn 10,000 days old at about 27 years and 4 months, and 1,000 weeks old at about 19 years and 2 months. Test candidate dates in the tool to pin down the exact day. And if you want a live on-screen countdown to the moment itself, the timer and stopwatch guide covers countdown timers that tick in real time.

Gregorian vs hijri age — why the numbers differ

The hijri (Islamic) calendar year is twelve lunar months — about 354 days, roughly 11 days shorter than a Gregorian year. Over a lifetime that gap compounds, so the same person's hijri age is a slightly bigger number: about 3% higher. A quick conversion: multiply your Gregorian age by 1.031 — someone who is 30 in Gregorian years is about 31 in hijri years.

Carbide's Age Calculator computes Gregorian age — the calendar used on official documents in most countries. If your paperwork uses the hijri calendar, as it does in Saudi Arabia, apply the 1.031 rule for a close estimate, and rely on an official hijri conversion for anything legally binding, since hijri months are set by lunar observation and can shift by a day.

Your birth date never leaves your device

Both tools are pure client-side math. The page loads once, then every calculation runs in your browser — your date of birth is never sent to a server, stored or logged. There is no account to create and no limit on how many dates you check.

The same on-device approach runs across Carbide's calculators: the BMI calculator (covered in the BMI guide), the percentage calculator (see the percentage, discount and tip guide) and the unit converter (see the unit conversion cheat sheet) all compute locally. For dates as for everything else: a calculator does not need your data — it needs your input, on your screen, and nothing more.

Frequently asked questions