Leap Year Calculator
Determine whether a given year is a leap year and calculate the next leap year.
This free online leap year calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
Enter any four-digit year to check
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Leap Year Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Leap Year Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Leap Year Calculator Formula
See calculator inputs for the governing equation
Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.
When to Use This Calculator
- •Use the Leap Year Calculator when you need accurate results quickly without the risk of manual computation errors or unit conversion mistakes.
- •Use it to verify calculations made by hand or in spreadsheets — an independent check can catch errors before they lead to costly decisions.
- •Use it to explore how changing input parameters affects the output — a quick way to develop intuition and identify the most influential variables.
- •Use it when collaborating with others to ensure everyone is working from the same numbers and applying the same assumptions.
About This Calculator
The Leap Year Calculator is a free, browser-based calculation tool for engineers, students, and technical professionals. Determine whether a given year is a leap year and calculate the next leap year. It implements standard formulas and supports both metric (SI) and imperial unit systems with automatic unit conversion. All calculations are performed instantly in your browser with no data sent to a server. Use this calculator as a quick reference and sanity-check tool during design, analysis, and learning. Always verify results against primary engineering references and applicable standards for any safety-critical application.
About Leap Year Calculator
The Leap Year Calculator determines whether any given year is a leap year according to the Gregorian calendar rules. Leap years occur every four years with specific exceptions for century years. Understanding leap years is important for date calculations, birthday planning (especially for February 29 births), and programming date logic correctly.
The Math Behind It
Formula Reference
Leap Year Rule
Leap = (year%4==0 AND year%100!=0) OR (year%400==0)
Variables: year = the year to check; divisible by 4 but not 100, unless also divisible by 400
Worked Examples
Example 1: Checking year 2100
Determine if the year 2100 is a leap year.
2100 is not a leap year. Despite being divisible by 4, the century-year rule excludes it because it is not divisible by 400.
Common Mistakes & Tips
- !Assuming every year divisible by 4 is a leap year (1900 was not).
- !Forgetting the 400-year exception (2000 WAS a leap year despite being divisible by 100).
- !Testing only for divisibility by 4 in programming, missing the century-year rules.
Related Concepts
Used in These Calculators
Calculators that build on or apply the concepts from this page:
Frequently Asked Questions
Why do we need leap years?
Earth's orbit takes approximately 365.2422 days. Without the extra day every four years, the calendar would drift about 24 days per century, eventually putting summer months in winter and vice versa.
Was 2000 a leap year?
Yes. While 2000 is divisible by 100 (which normally excludes it), it is also divisible by 400, which overrides the exclusion. The next century leap year will be 2400.