Age Calculator
Calculate age by date of birth in years, months, and days — or compare your age with another person.
Chronological Age Calculator
Chronological age is your exact age in years, months, and days from your date of birth to the selected date.
Age Calculator Methodology
Enter your birth date, choose the date to calculate from, and we’ll work out your age and related date details.
Inputs
Process
We calculate your age
Using exact calendar date logic
Results
Example age calculation
Date of birth
May 31, 1996
Target date
Today
Result
Age + next birthday
Age milestone
When will I turn a certain age?
Enter any age and get the exact date and weekday.
Past or future
How old will I be on another date?
Choose another date to see your exact age then, without changing your main result.
Another person
How old is someone else?
Enter their birthdate to calculate their age today, without changing your result.
Compare two people
What’s the age difference between me and someone else?
Compare your birthdate with theirs to see the exact gap and who is older.
Age projection
When I turn 55, how old will the other person be?
Calculator logic & edge cases
How this Age Calculator works
Detailed answers about the calculator’s logic, edge cases, and date-handling rules.
If I was born on Feb 29, which birthday does the calculator use in a non-leap year: Feb 28 or Mar 1? Read full answerShow less
This calculator uses Feb 28. If a year does not contain Feb 29, the calculator treats Feb 28 as the yearly anniversary for a Feb 29 birth date.
For someone born on Feb 29, 2000, the calculator shows 23 years, 0 months, 0 days on Feb 28, 2023. On Mar 1, 2023, it shows 23 years, 0 months, 1 day. In a leap year, the anniversary returns to Feb 29 itself, so Feb 29, 2024 is 24 years exactly.
The next-birthday result follows the same rule. If the next birthday falls in a non-leap year, it displays Feb 28 and identifies it as the observed date for the Feb 29 birthday.
This is the convention used by this calculator. Legal or official treatment of leap-day birthdays can vary by jurisdiction, so official age questions should follow the rule used by the relevant authority.
If I change the “age as of” date, what else in the result changes? Read full answerShow less
Everything that depends on the reference date moves with it. The calculator does not change only the large age number.
- Exact years, months and days
- Total days, whole weeks and whole months
- The next birthday on or after the selected date
- The birthday countdown and age being turned
- The next day milestone
Birth facts do not change. Your weekday of birth, birth year, generation and zodiac sign are properties of the birth date itself.
For example, someone born May 31, 1996 and calculated as of Jan 1, 2035 is 38 years, 7 months, 1 day old. Their next birthday from that reference date is May 31, 2035, 150 days away, when they turn 39.
If a second person is added, both people are calculated using the same selected date.
If I was born on Feb 29, am I 26 years old or only 6½? You are 26 years old. Age is based on completed calendar years since your birth date, not on how many Feb 29 dates have appeared. Read full answerShow less
For example, someone born on Feb 29, 2000 is 26 years, 7 months, 6 days old on Oct 5, 2026. Only six Feb 29 dates occurred between that birth date and Oct 2026, but that does not make the person six years old—or 6½ years old.
Dividing 26 by four only counts roughly how often leap day occurs. It is not how chronological age is calculated.
How does the calculator count months for a Feb 29 birthday in a non-leap year? The yearly anniversary and the monthly count use related but different rules. In a non-leap year, the Feb 29 yearly anniversary is clamped to Feb 28, but month counting still prefers the 29th. Read full answerShow less
After the yearly anniversary, the calculator counts completed months toward the 29th, using the last valid day only when a particular month does not contain that day.
This is why someone born on Feb 29, 2000 is 26 years, 7 months, 6 days old on Oct 5, 2026. The 26th anniversary is treated as Feb 28, 2026, but subsequent completed months are measured toward Mar 29, Apr 29, May 29 and so on. Seven full months are complete by Sep 29, leaving six additional days to Oct 5.
This distinction matters because simply measuring every month from Feb 28 would produce a different result. The calculator deliberately keeps the original birth day—the 29th—as the preferred day for month counting.
How does the calculator handle dates like Jan 31 when the next month has fewer days? It uses the last valid day of the shorter month, then returns to the original day when a later month contains it. Read full answerShow less
For a person born on Jan 31, 2000, after 23 completed years:
- Feb 28, 2023 = 23 years, 1 month, 0 days
- Mar 1, 2023 = 23 years, 1 month, 1 day
- Mar 30, 2023 = 23 years, 1 month, 30 days
- Mar 31, 2023 = 23 years, 2 months, 0 days
The calculator does not pretend that “Feb 31” exists. It clamps that monthly step to Feb 28, then uses Jan 31’s original day again when counting into March.
When a missing calendar day affects the displayed result, the calculator also shows a note identifying the adjustment—for example that Feb 28, 2023 was used because Feb 31 does not exist in that year.
How are total days, whole weeks, and whole months counted? The birth date is day 0. Total days are the number of calendar-day boundaries between the birth date and the selected “age as of” date. Read full answerShow less
A baby born on the selected date therefore shows 0 years, 0 months, 0 days and 0 total days. The following day is day 1.
Whole weeks are total days divided by 7 and rounded down. A baby who is six days old therefore has 0 whole weeks; at seven days old, the result becomes 1 whole week.
Whole months are based on completed calendar months, not an average number of days. The calculator takes the completed years × 12 and adds the remaining completed months.
As one tested example, Feb 29, 2000 to Feb 28, 2024 is 8,765 calendar days, 1,252 whole weeks, and 287 whole months. Leap days are naturally included in the calendar-day total.
What happens if my birthday is today—or exactly on the selected “age as of” date? The birthday counts as already reached. The calculator immediately includes the new completed year in your age. Read full answerShow less
Someone born on Mar 15, 1990, calculated on Mar 15, 2026, is 36 years, 0 months, 0 days old. If that selected date is the real current date, the birthday result reads “Today · Turning 36.”
If the same birthday is reached on a custom past or future “age as of” date, the result instead says “On this date · Turning 36.”
One day later, the same person is 36 years, 0 months, 1 day old, and the calculator begins counting toward the following birthday, when they will turn 37.
In other words, the birthday itself belongs to the new age, not the previous one.
What is the “next day milestone,” and what happens on the exact day? It shows the next round-number milestone based on total days lived. Exact milestone dates are shown as reached on that selected date rather than skipped. Read full answerShow less
The calculator uses 1,000-day steps below 5,000 days, then 5,000-day steps from 5,000 onward. The sequence therefore includes 1,000, 2,000, 3,000, 4,000, 5,000, 10,000, 15,000 days and so on.
If the selected date is exactly a milestone, the calculator does not jump immediately to the following one. At exactly 10,000 days old, it reports the 10,000-day milestone. If that selected date is the real current date, it says “Today: 10,000 days old.” For a custom past or future as-of date, it says “On this date: 10,000 days old.”
On the following day, the upcoming milestone becomes 15,000 days. A newborn at day 0 is not treated as having reached a milestone; the first upcoming one is 1,000 days.
Like the birthday result, the day milestone follows whichever “age as of” date you selected.
How is the exact age difference between two people calculated? The calculator measures directly from one birth date to the other. It does not subtract the two current ages and it does not simply subtract the birth years. Read full answerShow less
It takes the earlier birth date and counts forward to the later birth date in completed years, months and days using the same calendar rules as the main age calculation.
For example, May 31, 1996 and June 15, 2000 are 4 years, 0 months, 15 days apart.
The result does not change with time because the two birth dates themselves never change. Entering the people in the opposite order also produces the same gap; only which person is identified as older changes.
Month-end rules still apply. Jan 31, 2000 and Mar 1, 2000 are 0 years, 1 month, 1 day apart whichever person is entered first.
Why can Feb 29, 2000 and Feb 28, 2001 show as exactly 1 year apart even though 365 days passed? Because the calculator expresses the gap as a calendar age difference, not only as elapsed days. Read full answerShow less
A Feb 29 birthday uses Feb 28 as its yearly anniversary in a non-leap year. Therefore, when the calculator measures from Feb 29, 2000 to Feb 28, 2001, that later date is the first yearly anniversary under this calculator’s leap-day rule.
The calendar-age result is therefore 1 year, 0 months, 0 days apart, while the elapsed-day difference is still 365 days.
Both statements can be true at once because “1 calendar year of age” and “365 elapsed days” are different ways of expressing the interval. This is one reason an exact age difference should not always be treated as a conversion between years and a fixed number of days.
Why can two people born in the same year have different ages? Age depends on the full birth date, not just the year printed on it. Read full answerShow less
On Oct 5, 2026, someone born Jan 1, 1990 is 36 years, 9 months, 4 days old, while someone born Dec 31, 1990 is 35 years, 9 months, 5 days old.
Both were born in 1990, but the Dec 31 person has not yet reached their 2026 birthday.
The same effect can cross a year boundary. On Dec 31, 2026, someone born Dec 31, 1990 is 36 years exactly, while someone born Jan 1, 1991 is 35 years, 11 months, 30 days. Those two people were born only one day apart even though their birth years differ by one.
That is why subtracting birth years alone is not an exact age calculation.
What happens if one person had not been born yet on the comparison or projection date? The calculator never displays a negative age. In the normal comparison, both people must already have been born on the selected date. Read full answerShow less
If the second person had not yet been born on the selected “age as of” date, the main comparison is blocked and the calculator asks for a date that is the same as or later than both birth dates.
The projection tool is different. If you ask something like “When I turn 25, how old will they be?”, the projected date may legitimately occur before the second person’s birth.
In that case, the result says “The second person will not have been born yet.” If the projected date is exactly the second person’s birth date, their age is 0 years, 0 months, 0 days.
This lets the projection describe the chronology without inventing a negative age.
What happens when I switch between DD/MM/YYYY and MM/DD/YYYY after entering a date? The calculator preserves the meaning of the date instead of simply leaving the digits in the same positions. Read full answerShow less
A complete date such as 31/05/1996 in DD/MM/YYYY becomes 05/31/1996 in MM/DD/YYYY. It is still May 31, 1996, so the calculated age does not change.
Partly entered dates are also moved according to their day/month role rather than blindly interpreted as new numbers. A custom “age as of” date follows the same format switch.
This matters most with ambiguous dates. 04/05/2000 means May 4, 2000 in DD/MM/YYYY, but April 5, 2000 in MM/DD/YYYY.
The calculator starts new sessions in DD/MM/YYYY unless MM/DD/YYYY was already selected during the current browsing session, and displayed result dates are written out in words so you can confirm how the date was interpreted.
How old am I if I only know my birth year? A birth year alone usually gives two possible current ages, not one exact age. Read full answerShow less
Start by subtracting the birth year from the current year. If the birthday has already occurred this year, that is the person’s age. If the birthday has not happened yet, subtract one more year.
For example, someone born in 1990 during 2026 is 36 after their 2026 birthday and 35 before it.
An exact chronological age requires the month and day as well as the year. If only the birth year is known, the Birth Year Age Chart is the better tool because it shows ages by calendar year without inventing a month or day that was never provided.