Age Calculator

How old am I exactly? is a simple enough question but the true answer (not only the year, but the month and the day) takes more than mental arithmetic most people would like to do. This age calculator by date of birth works out your exact age in years, months, and days. It also doubles as an age calculator by year when you only need the age someone reached in a particular year, and it can show your age in total months, weeks, or days or count down to your next birthday. All the work is done on your local browser.

How to use the Age Calculator

1. Choose a date of birth (or any beginning date for measuring an interval instead of a literal age).

   

2. Leave the Age as of field to today or set it to a different date in the past or future, which can be helpful for eligibility checks or planning future dates.

   

3. Click “Use today” anytime to reset the second date to the present.

   

4. Read the result: exact number in years, number of months and number of days, and also in months, weeks and days.

   

5. See the next birthday panel to know the exact date, the number of days till next birthday and the day of the week.

   

6. Clear will clear both of the fields and the calculation is reset.

   

What is an age calculator?

An age calculator determines the time between two dates, usually a person’s date of birth and a selected end date. It can express the result in completed years, months, and days rather than simply giving an approximate number of years.

There are two things that people often get wrong about the result, both of which are worth understanding, not assuming the tool is wrong:

1. There are various cultural methods of age-counting. In most western systems, one’s age is incremented on their birthday. Age can be counted differently in some cultural or traditional systems. This calculator uses the standard birthday-based method, where a person’s age increases by one year on their birthday. This calculator is based on the standard birthday system that is used in most of the world.
2. There may be more than one possible answer to a month/day question at the end of a month. Since months vary in number of days, it is reasonable that when someone says “one month” from February 28th, they could reasonably mean either March 28th or March 31st. Both are defensible; every day of the year is calculated in the same way so the days figure may appear slightly different than if a hand calculation were performed in another way.

When you’d use this

Filling out a form or official document that requires an exact age, not just a birth year; determining whether you or someone you know is of a certain age (you’re in school, competing in some event, meeting a requirement for a legal age, etc); planning by a birthday or anniversary; figuring out someone’s exact age at a current or future date (when it’s not today); or just simply trying to satisfy a curiosity about how many days you’ve actually been alive.

Dos and Don’ts

Do:

1. For eligibility cutoffs which are based on a particular date, use the “age as of” field to verify the person’s age on that date, rather than today.
2. If you require an exact number of days or weeks for something (such as a countdown or age in days requirement), check the total-days or total-weeks value.
3. Accept a month/day result that is close to a month boundary, despite the fact that the result may be slightly different from a quick mental calculation – see above explanation.

Don’t:

1. Don’t assume that all age calculators provide the same number of months and days for a given pair of dates.
2. Mix up months or weeks with age in years, as they are the same length of time, but different ways to measure them, and mistakes can happen in a form or document when you mix them up.
3. Don’t use an approximate date of birth for official purposes. When accuracy matters, use the exact date shown on an official document such as a birth certificate or government-issued ID.

Good to know

The conventions used in different parts of the world to determine age are indeed different – most of the Western world uses the date of birth, though some traditional systems (such as an old Chinese one) use a fixed calendar date, meaning that the same individual may have different ages in different systems. This calculator is based on the “birthday method” which is adopted by most of the world. If you’re using months-and-days intervals, and you’re calculating exactly how many months and days are between two dates near the end of a month, e.g., between February 28th and March 31st, the interval, for this reason, may be ambiguous—it isn’t a problem with the calculation, just a peculiarity of date math. All of the processes on this page are executed in the browser, and no dates are sent nor saved.

FAQ: Age Calculator Questions