Age Calculator
Date & TimeEnter a date of birth. The calculator gives the exact age today in years, months and days, the age in months, weeks and days, the weekday of birth and how many days are left until the next birthday. Change the second date to find an age on any other day.
Step by step
October 6, 2026 - May 15, 1990 = 36 years, 4 months and 21 days
- First count the whole years from May 15, 1990 to October 6, 2026: 36 years.
- Then the whole months after that: 4 months.
- The days left over are 21 days, so the age is 36 years, 4 months and 21 days.
- Between the two dates lie 13,293 days, which is 1,899 weeks. Whole months in total: 436 months.
- The next birthday is May 15, 2027, in 221 days.
Once every entry is valid, you’ll see each step of the calculation here.
Formula
- date of birth
- the day the person was born
- second date
- today, or any date you choose
- age
- completed years, months and days
How it works
The calculator counts the way people count birthdays. First it counts the whole years from the date of birth to the second date, then the whole months after the last birthday, then the days that are left. Someone born on May 15, 1990 is 36 years, 4 months and 21 days old on October 6, 2026: 36 years to May 15, 2026, 4 months to September 15 and 21 more days to October 6.
The age in days is the plain count of calendar days between the two dates, including every leap day in between. The age in weeks splits those days into whole weeks and days left over, and the age in months is the whole years times 12 plus the extra whole months. The weekday of birth comes from the same calendar arithmetic.
Someone born on February 29 has a real birthday only in leap years. In other years the calculator counts the birthday on February 28, the last day of February. Rules for legal purposes differ: some count March 1 instead. For days between any two dates, not just from a birth date, use the days between dates calculator.
The formula
Months have 28 to 31 days, so an age in months and days depends on which months lie between the dates. The calculator steps month by month on the real calendar. A step onto a day that does not exist, such as February 30, lands on the last day of that month.
Ages in the US are counted in completed years: you turn 18 on your 18th birthday, not before. The day of birth itself is not counted as a day already lived, so a baby is 0 days old on the day it is born.
Example
How old is someone born on May 15, 1990 on October 6, 2026?
- Whole years: from May 15, 1990 to May 15, 2026 is 36 years.
- Whole months: from May 15 to September 15, 2026 is 4 months; then 21 days to October 6.
- Age: 36 years, 4 months and 21 days, or 13,293 days in total. The next birthday is May 15, 2027, in 221 days.
On October 6, 2026 the age is 36 years, 4 months and 21 days, which is 13,293 days since birth. The next birthday is May 15, 2027, in 221 days, when the age will be 37 years.
Load this example into the calculatorFrequently asked questions
How do I calculate my exact age?
Count the whole years from your date of birth to today, then the whole months since your last birthday, then the remaining days. Born on March 10, 2000, you are 26 years, 6 months and 26 days old on October 6, 2026.
How many days old am I?
Enter your date of birth and read “Age in days”. A 30-year-old has lived about 10,957 days, since 30 years have 7 or 8 leap days. The calculator counts the exact calendar days, leap days included.
When does someone born on February 29 have a birthday?
In leap years on February 29. In other years this calculator counts the birthday on February 28. For legal purposes such as a driver’s license, agencies and states do not all agree on February 28 or March 1, so check the rule that applies to you.
Can I calculate an age on a past or future date?
Yes. Change “Age on this date” to any date after the date of birth. This answers questions like how old someone was at graduation, or how old a child will be on the first day of school.
What day of the week was I born?
The calculator shows it under “Born on a”. It comes from the same calendar that counts the days: May 15, 1990, for example, was a Tuesday.
- Age (Wikipedia)
- Gregorian calendar (Wikipedia)
- February 29 (Wikipedia)