Age Calculator

Instructions for using this Age Calculator

This age calculator only requires less than 5 seconds to use! Type your date of birth in the box above and, if you are interested in showing your age at a date other than today, change the "calculate age as of" box. Enter your age and receive it immediately in years, months, weeks, days, hours and minutes – it's completely free and doesn't require you to register, enter your email address or download an app.

It can be used in reverse too! If you have a person's age but not the exact date of birth, then enter the known age and a reference date and the calculator will calculate the range of possible birth date. This can be especially helpful for genealogy research, completing historical records, or approximate birth year verification.

How can an age calculator work?

An age calculator is an exact arithmetic program that takes off your birthdate from a date set (typically the current date), instead of merely approximating it. This is much more important than people think: Calendars are not evenly organized. There are 30 days in the month of May, but the number of days in the month of June is different. May has 30 days in a month, June has 31 days in a month (approximately).

The actual logic in calculating the correct age is as follows:

• Calculate the difference between the year you want and the year you were born. This provides an approximate age.
• See if the birthday has already come and gone this year. If the current day and month are before the person's birth month and day, then subtract 1 year from the rough total.
• Find the number of months and days to be added to the last birthday to reach the target date.
• Implement leap year logic to ensure that people born on a February 29 in a non-leap year are treated appropriately.

A calculator which omits any of steps 2-4 will retort silently with an age off by up to a year — which is a common error in manual calculations, and a common error in poorly designed calculators.

February 29th Birthdays and Leap Years

You can still use this calculator if you were born on a leap day, and get a perfect, standard result — not an approximation. Like most civil registration systems around the world, February 28 is considered as the legal age-increment date in a non-leap year. So someone born on February 29, 2000 turns 25 on February 28, 2025, and turns 26 on February 29, 2028, when the leap day returns.

The simple leap year rule: if a year is divisible by 4, it is a leap year, except that century years, which have the form of 100 + N where N is any number, are not leap years unless N is divisible by 400. This calculator does that automatically for you, so no need to think about it.

The world has various methods of determining age

There are several different age-counting systems around the world.

Though most people would think that the word "age" translates to one number, that's not the case throughout the world. This calculator is based on the international (western) age system, which is the age system used in almost all legal, medical and administrative situations around the world, and is the age system used for the majority of people, including most of you.

There are two additional systems in use in parts of the world that are used in a cultural way:

• The traditional Korean and Chinese method of counting age: In the traditional Korean and Chinese way of counting age, the age of a person is counted from birth, and all people's ages go up on the first day of each year, instead of by their birthdays. With this in place, a child would turn "2" within weeks of his or her birth if born in December.
• Count-inclusive: Some count based on the year of life one is living in, not on how many years one has lived, thus a person in their 21st year of life may be called "20" in a western culture but be differentiated elsewhere in a count-inclusive system.

Since that can be confusing for readers who have family elsewhere, if you need to use a different system, you should note it on the page.

Common Uses for an Age Calculator

There are more than just curiosity motives for using an age calculator. The more typical applications are:

• Legal and administrative documents: job applications, visas and government documents often require an exact age or date of birth verification.
• Date of birth cutoffs: (for example, a child needs to be 5 years old on September 1st and older to be eligible for kindergarten; 6 years old and older to be eligible for first grade) are used by many school districts to place children in a grade.
• Exact formula dosing: Certain medicines are given in precise doses according to age (usually in months or days), especially for babies.
• Retirement and Pensions: The age at which you can retire, and the amount of money you receive for your pension or Social Security, and whether you can access certain IRA withdrawal rules, often depends on the exact age — sometimes the exact month.
• Insurance Premiums: Premiums for life insurance and health insurance often change at specific age thresholds, so your exact age may have a financial impact on your insurance.
• Research, genealogy: The use of age calculations based on historical data or estimation of years of birth from known ages is useful to assist in making accurate family trees.
• Fun metrics: From "how many days old is my baby" to "how many days until I'm 10,000 days old," people just love seeing the passing of significant numbers.

Western & Chinese Zodiacs Explained

In addition to basic age metrics, our calculator evaluates your birth year and day to determine both astrological zodiac profiles:

• Western Zodiac: Determined by your month and day of birth (Aries, Taurus, Gemini, etc.), mapping your celestial profile.
• Chinese Zodiac: Determined by your year of birth in the Chinese lunar calendar (Dragon, Snake, Horse, etc.), following a 12-year animal cycle.

Use Age Calculator or Manual Calculation

You can do it by hand by subtracting the year, month and day from your birth and subtract the same from today, but you can make little mistakes (like does the current, unfinished year count, how do you handle month length differences, etc.). That's where an age calculator comes in handy, as it's the only way to get accurate results when it comes to legal, medical, or financial matters.

Frequently Asked Questions