Age Calculator

Age calculator at a glance#

How do you calculate age from a date of birth?#

To calculate someone's age, you find the full years since their birth date, then add the full months, and finally the remaining days. You simply input the date of birth and the date for which you want to calculate the age. The calculator handles the counting for you, including leap days. The result also provides the total time span in months, weeks, days, hours, minutes, and seconds.

How old is someone born on April 29, 1990?#

As of October 28, 2026, an individual born on April 29, 1990 is 36 years, 5 months, and 29 days old, which totals 13,331 days. They will turn 37 on April 29, 2027, exactly 183 days later.

What is chronological age?#

Chronological age refers to the time elapsed since birth, expressed in years, months, and days according to the calendar. The age in full years aligns with your age at the last birthday, which is what most forms require. In this particular instance, the chronological age is 36 years, 5 months, and 29 days, with an age in whole years of 36.

What an exact age means#

In everyday conversations, age is the count of birthdays celebrated. The UK census records age at last birthday in the same way. An exact age, however, includes the months and days since the last birthday, so two people aged 36 could be almost a year apart.

The example featured here uses a birth date of April 29, 1990 and an age date of October 28, 2026. The last birthday was on April 29, 2026, marking the 36th birthday. Since that point, 5 complete months and 29 days have gone by.

How to calculate age by hand#

There are two methods to determine the years, months, and days, both giving the same result.

Method 1: count forward from the birth date#

Begin at the birth date and move forward in the largest increments possible before reaching the age date. First add full years, then full months, and finally count the remaining days.

• Add 36 years to April 29, 1990 to arrive at April 29, 2026. Adding another year would exceed the age date.
• Add 5 months to reach September 29, 2026. A sixth month would lead to October 29, which is one day too far.
• Count the days from September 29 to October 28, 2026. September has 30 days, so there is 1 day to September 30 and 28 more entering October, totaling 29 days.

This results in an age of 36 years, 5 months, and 29 days.

Method 2: subtract the dates column by column#

Write the age date and birth date as year, month, and day, and subtract each column from right to left, borrowing as needed when a column would otherwise result in a negative number.

• Days: 28 minus 29 doesn't work, so borrow a month. The month before October is September, which has 30 days. This makes the day column 28 + 30 = 58, and 58 minus 29 equals 29 days.
• Months: October initially had 10, and after borrowing a month it becomes 9. Subtracting 9 minus 4 gives 5 months.
• Years: 2026 minus 1990 is 36 years.

When the month column is negative, borrow a year and add 12 to the months instead.

Your age in days, weeks, hours, and seconds#

Counting days provides a consistent measure unaffected by month borrowing, making it the most straightforward way to compare two ages precisely. From April 29, 1990 to October 28, 2026, the span is 13,331 days. The calculator converts this span into 437 months and 29 days, 1,904 weeks and 3 days, 319,944 hours, 19,196,640 minutes, and 1,151,798,400 seconds.

The first line of the result breaks down the remaining days into weeks, so the reading becomes 36 years 5 months 4 weeks 1 day, equivalent to 5 months and 29 days. Two small calendars below the result show the birth date and the age date.

Leap days accumulate. The 36 years between April 29, 1990 and April 29, 2026 include 9 leap days, totaling 13,149 days instead of 36 times 365. A milestone like being 10,000 days old falls on a specific date, which in this example is September 14, 2017.

Age on any date#

The second field need not be set to today. You can set it to a past date to determine how old someone was at a particular event, or to a future date to predict your age. The shortcuts for Yesterday, Today, and Tomorrow make this quick.

These fields also calculate the age difference between two individuals. By inputting the older person's birth date as the birth date and the younger person's birth date as the age date, you find the age gap, which will remain constant throughout their lives.

If you know the birth time, the time duration calculator counts the days, hours and minutes between two dates and times, and the hours and minutes calculator gives the same span in total hours.

Leap years and February 29 birthdays#

A leap year includes February 29. Under the Gregorian calendar, a year is a leap year if divisible by 4, except for century years, which must also be divisible by 400. Thus, 2000 was a leap year, whereas 2100 will not be.

For someone born on February 29, that date only recurs in leap years. In other years, their birthday is typically observed on February 28 or March 1, with variations depending on the country and context, so check the local rules for legal matters. The total day count remains unaffected, counting every real day between the two dates, including each February 29.

Why age calculators can disagree by a few days#

While the years and total days are fixed, the division into months and days can vary between tools when the birth day occurs late in a month. Borrowing a month involves adding that month's days, and months range from 28 to 31 days. Thus, tools borrowing from different months may give different day counts. The calculator above borrows the birth month's length. For March 28, 1981 to March 1, 2023 it shows 41 years 11 months 4 days, while counting forward gives 41 years 11 months 1 day. Both give 15,313 days. In this example, both September and April have 30 days, so all methods agree on 29 days. When two results differ, the total day count resolves the discrepancy.

Where an exact age is used#

• Forms and applications requesting age in whole years or on a specific date.
• Verifying eligibility based on age at a cutoff date, for example, in youth sports seasons or school years.
• Milestones and celebrations such as a 10,000th day or a half birthday.
• Precisely comparing two ages, like for siblings, twins born on either side of midnight, or historical figures.

Age in 2026 by birth year#

Subtract the birth year from 2026 for the age on this year's birthday, and take one off before the birthday comes around.

Sources#

• Scotland's Census, Age (age at last birthday, derived from date of birth)
• Hong Kong Observatory, Leap Year (the Gregorian leap year rule)

Frequently asked questions#

How do I calculate my age in days?#

Simply enter your date of birth and today's date. The result's days line will show your age in days, counting every leap day. For example, someone born on April 29, 1990 is 13,331 days old as of October 28, 2026.

How old will I be on a future date?#

To find out, insert the future date in the second field. The result will display your age on that day in years, months, and days, alongside the totals in weeks, days, and smaller units.

How do I find the age difference between two people?#

Input the birth date of the older person first, followed by the younger person's birth date as the age date. The result is the gap in years, months, and days, which remains constant as both grow older.

How many days until my next birthday?#

Count the days from today to your upcoming birthday. From October 28, 2026 to April 29, 2027 is 183 days. While the age calculator provides your age, for a countdown, use a date calculator with today and your birthday as inputs.

Does the age calculator count leap years?#

Yes, every February 29 within the specified range counts as a real day. In the example, the 36 years encompass 9 leap days.

How is age counted for someone born on February 29?#

Age in whole years increases annually like everyone else's, despite the birth date appearing only in leap years. For exact months and days, results may vary by a day around late February, so use the total day count for absolute accuracy.