Leap Year Checker
Check whether any year is a leap year, and see the exact rule that decides it.
How this is calculated
A year is a leap year if it's divisible by 4. The exception is century years (divisible by 100): those are only leap years if they're also divisible by 400. That's why 2000 was a leap year but 1900 and 2100 are not, the extra rule keeps the calendar aligned with the actual solar year over long stretches of time. For the full story on why this rule exists at all, see Why Do We Have Leap Years?
Frequently asked questions
How do I know if a year is a leap year?
A year is a leap year if it's divisible by 4. The exception is century years (years divisible by 100): those are only leap years if they're also divisible by 400. That's why 2000 was a leap year but 1900 and 2100 are not.
Why are century years different?
The simple every-4-years rule adds slightly too many extra days over centuries, so the Gregorian calendar removes 3 leap years every 400 years by skipping century years that aren't divisible by 400. That keeps the calendar aligned with the actual solar year.
How do I list all leap years between two years?
Switch to the "List years in a range" tab, enter a start and end year, and select Check. The result shows the count of qualifying leap years and lists each one, up to a 500-year range.
Sources
- NASA Jet Propulsion Laboratory, "Doing the Math on Why We Have Leap Day"
- US Naval Observatory Astronomical Applications Department, "Leap Years"
Built and maintained by Ready Utilities, founded by Cedrick Reese, a retired veteran and web developer. Every formula and convention on this site is checked against real, current sources before publishing. This calculator runs entirely in your browser, nothing you enter is sent anywhere. Spot something that looks wrong? Let us know.