Age Calculator by Date of Birth — Find Your Exact Age in Years, Months & Days

What Is an Age Calculator and How Does It Help?

An age calculator works out the time between a date of birth and another date, usually today, and gives the answer in years, months and days. Someone born on 15 May 1990 is, on 20 August 2026, 36 years, 3 months and 5 days old.

Counting by hand means dealing with months of different lengths and leap years, which is where mistakes creep in. Enter the two dates here and the result, the total days lived and the next birthday all update at once. If you also want to check health numbers for the same person, the BMI Calculator works the same way in your browser.

Why People Calculate Age

Age comes up in forms, eligibility rules, school admissions and celebrations. These are the cases where an exact figure matters most.

Example Ages and How They Break Down

These examples show how the same method is applied to different dates. You can type any of them into the calculator to check the result.

How to Use the Age Calculator

1. Choose the date of birth. You can type it or pick it from the calendar.
2. Leave “Age at the date of” on today, or pick another date to see the age on that day, such as a past or future date.
3. Read the exact age in years, months and days, then check the progress bar for the next birthday.
4. Open the statistics for total months, weeks, days, hours, minutes and seconds, the weekday of birth and the zodiac sign.
5. Switch the list at the bottom between Milestones and Next birthdays, then copy the result or the statistics.

How to Calculate Age by Hand

The method is the same one the calculator follows. Subtract the birth date from the later date one part at a time, and borrow when a part comes out negative.

• Subtract the years. 2026 minus 1990 gives 36, which is correct only if the birthday has already passed this year.
• Subtract the months. August minus May gives 3. If the result is negative, take one year off and add 12 months.
• Subtract the days. 20 minus 15 gives 5. If the result is negative, take one month off and add the number of days in the month before the later date. Around month ends this can differ by a day or so from the calculator, which counts forward from the birth date.
• Check the leap years. A year has 366 days when it divides by 4, except century years, which must divide by 400. So 2000 was a leap year and 1900 was not.
• For total days, count the days between the two dates directly rather than multiplying years by 365, which loses the leap days.

Age Calculator Formula for Excel and Google Sheets

To calculate age from a date of birth in a spreadsheet, put the birth date in cell A2 and use the DATEDIF function, which works in both Excel and Google Sheets. Replace TODAY() with another date or cell to get the age as on that date.

The "MD" part can be off by a day or so around month ends in some spreadsheet versions, so compare the result with this calculator when the exact day matters.

Chronological Age Calculator: What It Means

Chronological age is the time that has passed since birth, written in years, months and days. It is the age used for school entry, sports categories and the norm tables of many child development and psychological assessments. The exact age shown above is the chronological age on the date you pick.

Chronological age is not the same as corrected age. For a baby born early, corrected age subtracts the weeks of prematurity and is usually used only in the first two years or so. This calculator does not apply that adjustment, so follow the instructions of the test or your child’s doctor when it applies.

A Practical Guide to Age Calculation

Age sounds simple, yet a few details change the answer. It helps to know the choices this calculator makes when you use the result for a form or a deadline.

How This Age Calculator Works

When either date changes, the page checks that the birth date is not after the “age at” date, calculates the age, finds the surrounding birthdays and refreshes every statistic and list in one go.

Simple Tips for Calculating Age

• Use the “age at” date to find an age on a specific day, such as an application deadline, the first day of school or a future event.
• Check the day, month and year order on your device’s date picker, since some regions show the day first and others the month first.
• For people born on 29 February, work out the age on both 28 February and 1 March if a rule depends on the exact day.
• Use total days when you need a precise length of time, because months and years differ in length.
• For a reading goal or a lesson plan that depends on time, the Reading Time Calculator turns a word count into minutes.

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