Age Calculator
Calculate your exact age in years, months, days, hours, and seconds.
Age calculator
Updates as you change datesBirthday schedule
| Age | Date | Day | Days from birth | Life progress |
|---|
Formula
- Y, M, D
- Year, month, and day components of each date
- b
- Subscript for birth date
- t
- Subscript for target ("as of") date
- Raw year difference = —
- Raw month difference = —
- Raw day difference = —
- Borrow from shorter month if days < 0 → —
- Final age = —
When the target day is earlier in the month than the birth day, we borrow a month using the number of days in the previous calendar month — so the result always reflects completed calendar months, not a running fraction of 30. Feb 29 birthdays fall back to Feb 28 in non-leap years for "next birthday" logic.
Examples
How It Works
Month lengths vary (28, 29, 30, or 31 days), which affects the day count. If you were born on January 31 and we are calculating your age on March 2, the "remaining days" step must account for February having only 28 or 29 days. The calculator handles this by borrowing from the previous month's actual length. Leap year birthdays (February 29) receive special treatment: in non-leap years, the anniversary falls on February 28.
It is worth noting that not all cultures count age the same way. The Western system — used by this calculator — starts at 0 and increments on each birthday. In the traditional East Asian system, a baby is considered 1 year old at birth and gains a year every Lunar New Year, meaning someone could be "two" by Western reckoning when they are only a few weeks old. South Korea officially switched to the Western system in 2023.
Tips & Best Practices
Frequently Asked Questions
How is exact age calculated?
The calculator computes the difference between your birth date and today by counting complete years, then remaining months, then remaining days. It correctly handles varying month lengths and leap years.
What about people born on February 29?
Leap year birthdays are handled correctly. In non-leap years, the calculator treats March 1 as the anniversary date. The total day count always reflects the actual number of days elapsed.
How do different cultures count age?
In Western cultures, age starts at 0 and increments on each birthday. In some East Asian cultures, babies are considered 1 at birth and gain a year at the Lunar New Year. This calculator uses the Western system by default.
Can I calculate age between two arbitrary dates?
Yes. Enter any start date and end date to calculate the exact duration between them. This is useful for determining the age of buildings, contracts, or time spans between historical events.
What is chronological vs biological age?
Chronological age is the time elapsed since your birth — what this calculator measures. Biological age reflects how well your body is functioning compared to the average for your chronological age, based on markers like telomere length, cardiovascular fitness, and metabolic health. Two people who are both 50 chronologically may have very different biological ages.
How many days old am I?
Enter your birth date and today's date into the calculator to see the exact total days count. For a quick estimate, multiply your age in years by 365.25 (accounting for leap years). For example, a 30-year-old has been alive for approximately 10,958 days.
What zodiac sign am I?
Your Western zodiac sign is determined by your birth date: Aries (Mar 21–Apr 19), Taurus (Apr 20–May 20), Gemini (May 21–Jun 20), Cancer (Jun 21–Jul 22), Leo (Jul 23–Aug 22), Virgo (Aug 23–Sep 22), Libra (Sep 23–Oct 22), Scorpio (Oct 23–Nov 21), Sagittarius (Nov 22–Dec 21), Capricorn (Dec 22–Jan 19), Aquarius (Jan 20–Feb 18), Pisces (Feb 19–Mar 20).
How is age calculated for legal purposes?
In most legal systems, you reach a new age at the very start of your birthday (midnight). Some jurisdictions, however, consider you to have reached a given age on the day before your birthday — this matters for determining eligibility for voting, driving, drinking, or retirement on specific dates. For leap year birthdays, laws vary: some jurisdictions treat March 1 as the legal birthday in non-leap years, while others use February 28.
Why does age calculation get tricky with months of different lengths?
Months have 28 to 31 days, so 'one month' is not a fixed duration. If you are born on January 31, one month later could be February 28 (or 29 in a leap year). This calculator handles this by borrowing from the previous month's actual length when the birth day exceeds the number of days in the current month, ensuring an accurate day count.
What is the Korean age system?
The traditional Korean age system counted everyone as 1 at birth and added a year every January 1, regardless of actual birthday. This meant a baby born on December 31 would be considered 2 years old the very next day. In June 2023, South Korea officially adopted the international (Western) age system for legal and administrative purposes, though the traditional system is still used informally.