Leap Year Calculator
Enter any year below to instantly check whether it's a leap year.
How This Is Calculated
A year is a leap year if it's divisible by 4, unless it's also divisible by 100 — in which case it needs to be divisible by 400 too.
A common mistake is stopping at the divisible-by-4 test and never checking the century exception. Most divisible-by-4 years really are leap years, which is exactly what makes the rare century exceptions easy to get wrong when they come up.
Worked example
Is 2024 a leap year?
2024 ÷ 4 = 506, with no remainder, and it's not a century year.
Yes, 2024 is a leap year.
Is 1900 a leap year?
1900 ÷ 4 = 475, with no remainder — so the basic test says yes. But 1900 ÷ 100 = 19, also with no remainder, so it's a century year, and 1900 ÷ 400 = 4.75 doesn't divide evenly.
No, 1900 is not a leap year — the century exception overrides the divisible-by-4 result.
Keep going
- A leap year's extra day can shift a date difference calculation by one; the date difference calculator accounts for that automatically across any two dates. Date Difference Calculator
Frequently Asked Questions
What is the rule for leap years?
A year is a leap year if it's divisible by 4, unless it's also divisible by 100 — in which case it's only a leap year if it's also divisible by 400. This extra rule keeps the calendar aligned with Earth's actual orbit, which is slightly less than 365.25 days.
Why was the year 2000 a leap year but 1900 wasn't?
1900 is divisible by 100 but not by 400, so the century exception makes it a regular year. 2000 is divisible by both 100 and 400, so the exception doesn't apply and it's a leap year.
How often do leap years occur?
On average, once every 4 years, except century years not divisible by 400 are skipped — so there are 97 leap years every 400 years instead of the 100 you'd get from the simple divisible-by-4 rule alone.
Will 2100 be a leap year?
No. 2100 is divisible by 4 and by 100, but not by 400 (2100 ÷ 400 = 5.25), so the century exception applies and it stays a regular 365-day year — the same situation as 1900, 1800, and 1700.
Why does the calendar need this extra rule at all?
Earth's orbit takes about 365.2422 days, not exactly 365.25. Adding a leap day every 4 years overcorrects slightly, so dropping 3 leap days every 400 years (the century exception) keeps the calendar much more closely aligned with the actual solar year over long stretches of time.
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