Age Calculator
Accurately compute age from date of birth.
Find your exact age in years, months, and days — accurate to the day. Enter your date of birth and optionally choose a custom "as of" date to calculate age at any point in time, past or future. Leap years are handled automatically. Includes Korean man-nai (만 나이) for Korean administrative contexts.
Age Calculator
Leave as today, or enter any past/future date
Examples
Standard age calculation
Born January 1, 2000 — calculating age as of January 1, 2025.
→ 25 years, 0 months, 0 days — Total: 9,131 days lived
Leap year birthday (Feb 29)
Born February 29, 2000 — calculating age as of February 28, 2025 (non-leap year).
→ 25 years, 0 months, 0 days (Feb 28 used as birthday in non-leap years)
Age at a past date
Born June 15, 1990 — how old were they on January 1, 2000?
→ 9 years, 6 months, 17 days
Age at a future date
Born March 25, 1991 — how old will they be on March 25, 2031?
→ 40 years, 0 months, 0 days
Birthday has not yet occurred this year
Born December 1, 1990 — calculating age as of March 25, 2026.
→ 35 years, 3 months, 24 days (birthday in December not yet reached)
Tips
- ✓Use the "As of Date" field to check your age on a specific date — past or future.
- ✓Leap year birthdays (Feb 29) are automatically treated as Feb 28 in non-leap years.
- ✓Korean man-nai (만 나이) shown in results is now the official Korean standard since June 2023.
- ✓For school enrollment eligibility checks, set the "As of Date" to the cutoff date used by the institution.
- ✓For retirement planning, set the "As of Date" to your planned retirement date to confirm your age.
- ✓For official document verification, confirm the exact age definition used by the issuing authority.
Frequently Asked Questions
How is age calculated?
Age is calculated by finding the difference between your birth date and the target date. First, complete years are counted. Then remaining months and days are calculated from the last birthday to the target date. Leap years are handled automatically — February 29 birthdays are treated as February 28 in non-leap years.
Is the result accurate to the day?
Yes. The calculator counts complete years, then remaining months, then remaining days — all based on calendar months, not fixed 30-day months. The result is accurate to the exact calendar day.
Can I calculate age at a past or future date?
Yes. Use the "As of Date" field to set any date — past, present, or future. For example, enter a future date to find how old you will be on your next birthday or retirement date.
What happens if my birthday has not occurred yet this year?
If your birthday has not yet passed in the current year, the calculator correctly shows one year less. For example, if you were born on December 1, 1990 and today is March 25, 2026, your age is 35 (not 36).
How are leap year birthdays handled?
If you were born on February 29, the calculator uses February 28 as your birthday in non-leap years. This matches how most countries handle leap-day birthdays for legal and administrative purposes.
What is Korean man-nai (만 나이)?
Man-nai (만 나이) is the international-standard counting method used officially in Korea since June 2023. In this system, you are 0 at birth and gain one year on each birthday — the same as the global standard. This replaced the older Korean age systems (세는 나이, 연 나이) for official use.
Can I use this calculator for official documents?
This calculator provides accurate results based on calendar arithmetic. However, for official legal, immigration, insurance, or government documents, always verify with the issuing authority — some systems define "age" slightly differently (e.g., age as of December 31 of a given year).
Why do age systems differ between countries?
Different cultures count age differently. The international standard (used in most countries) starts at 0 at birth and adds 1 on each birthday. The traditional Korean system (세는 나이) starts at 1 at birth and adds 1 every January 1. Korea officially switched to the international standard (만 나이) in June 2023.
What does "total days lived" mean?
Total days lived is the absolute number of days from your birth date to the as-of date. This counts every calendar day, including leap days. It is useful for milestone tracking or insurance actuarial purposes.
How do I calculate age at a specific past date?
Enter your birth date in the "Date of Birth" field, then set the "As of Date" field to the specific past date you want. The calculator will show your age at that point in time.