To calculate your exact age, count the full years since you were born, then the full months since your last birthday, then the days left over. Someone born on May 15, 1990 is 36 years, 4 months and 18 days old on October 3, 2026. They have been alive for 13,290 days, and their next birthday is 224 days away.
Our free age calculator works all of this out from a date of birth: your age in years, months and days, the total number of days you have been alive, and how many days remain until your next birthday. This guide shows the method behind it, how leap-day birthdays are handled, and other ways to express an age.
How to calculate age from a date of birth
Age is counted in three steps, from the largest unit to the smallest. Each step starts where the previous one stopped.
Worked example: born May 15, 1990, measured on October 3, 2026
- Years. Subtract the birth year from the current year: 2026 − 1990 = 36. The birthday, May 15, has already passed this year, so the person has completed 36 full years. If it had not passed yet, you would subtract 1.
- Months. Count the full months from the last birthday, May 15, 2026. June 15, July 15, August 15 and September 15 make 4 months.
- Days. Count from September 15 to October 3. September has 30 days, so that is 15 days to the end of September plus 3 days into October: 18 days.
The result is 36 years, 4 months and 18 days, which is what the calculator shows.
The quick check for whole years
If you only need someone's age in years, compare today's month and day with their birthday. If the birthday has come this year, the age is the current year minus the birth year. If not, it is one less. Someone born in 1990 is 36 during 2026 after their birthday and 35 before it.
Your age in days, weeks and months
The calculator's total days figure counts every day from your date of birth up to today. From there, other units are simple division:
- Weeks: 13,290 ÷ 7 = 1,898 weeks and 4 days.
- Months: 36 years × 12 + 4 months = 436 full months.
- Hours: 13,290 × 24 = 318,960 hours, give or take the hours of today.
Day-count milestones
Some people celebrate round numbers of days as well as birthdays. These are the approximate ages at which they fall, using an average year of 365.2425 days:
| Milestone | Approximate age |
|---|---|
| 10,000 days | 27.4 years |
| 1 billion seconds (11,574 days) | 31.7 years |
| 15,000 days | 41.1 years |
| 20,000 days | 54.8 years |
| 25,000 days | 68.4 years |
For the person born on May 15, 1990, day 10,000 was September 30, 2017. Watch the total days alive figure in the calculator to see how close you are to your next milestone.
Leap-day birthdays
People born on February 29 only have a real birthday every four years. In common years the age calculator moves the birthday to March 1. Someone born on February 29, 2000 sees 26 years, 11 months and 30 days on February 28, 2027, with 1 day to go, and turns 27 on March 1.
Legal rules for leap-day birthdays differ from country to country. Some treat February 28 as the birthday in common years and others use March 1, so check the local rule when an exact legal age matters, such as for a license or a contract.
How to use the age calculator
- Open the age calculator.
- Pick a Date of birth. The date picker stops at today, because a future date has no age. If the field is cleared or holds an unusable date, the calculator says so instead of showing a number.
- Read your Age in years, with the extra months and days under it.
- Read Total days alive and Next birthday in, the number of days until your next birthday. On the birthday itself the countdown shows 0 days.
The calculator measures up to today's date in UTC (Coordinated Universal Time). Late in the evening in the Americas, or early in the morning in Asia and Australia, that date can be one day off your local date, so the days figures may differ by one.
Practical uses
- Forms and applications. Many forms ask for an exact age or check an age limit. The calculator gives a precise answer instead of a mental estimate.
- Age on a specific date. To find an age on a date other than today, such as a school entry cutoff or an election day, use the date difference calculator. Enter the date of birth as the start date and the cutoff as the end date; its years, months and days breakdown works the same way.
- Planning a birthday. Use the countdown to see how much time you have, then find the weekday the birthday falls on in the year calendar.
- Children's ages. Babies and toddlers are often described in months. Multiply the years by 12 and add the months: 1 year and 7 months is 19 months.
Frequently asked questions
How do I calculate my exact age?
Count the full years since your birth date, then the full months since your last birthday, then the remaining days. Someone born on May 15, 1990 is 36 years, 4 months and 18 days old on October 3, 2026.
How old am I if I was born in 1990?
In 2026 you are 36 if your birthday has already passed this year and 35 if it has not. Enter your full date of birth in the age calculator to get the exact months and days as well.
How many days old am I?
The age calculator shows your total days alive as soon as you enter your date of birth. Someone born on May 15, 1990 is 13,290 days old on October 3, 2026.
How is age calculated for someone born on February 29?
The age calculator treats March 1 as the birthday in years without a February 29, so a leap-day baby turns a year older on March 1. Legal rules vary by country, and some use February 28 instead.
Can I calculate my age on a past or future date?
The age calculator always measures to today. For any other date, use the date difference calculator with your date of birth as the start date and the date you need as the end date.
Why does the age calculator not accept a future date?
A date of birth after today has no age to measure, so the calculator asks you to pick a real date on or before today.