Leap Year Calculator: The Complete Guide
Check whether any year is a leap year. Enter a year to see if it has 366 days, why, and when the next leap year falls — using the complete Gregorian calendar rule.
Who the Leap Year Calculator is for
Students, developers, and the curious who need to confirm leap years and the rule behind them.
How to use the Leap Year Calculator
- Type your values into the fields above — pick your currency or units where the calculator offers them.
- Results update automatically as you type; there's no submit button and nothing is sent to a server.
- Adjust any input to compare scenarios, then copy the result with a single click.
How it works
A year is a leap year if it's divisible by 4, except century years, which must also be divisible by 400. So 2000 and 2024 are leap years, but 1900 and 2100 are not.
Features
- Leap year check
- Days in the year
- Next leap year
- Full Gregorian rule
The leap year rule
Leap years keep the calendar aligned with Earth's orbit, which takes about 365.2425 days. The rule: a year is a leap year if divisible by 4, but century years (like 1900) are only leap years if also divisible by 400. That extra rule is why 2000 was a leap year and 1900 wasn't — a detail that catches many people out.