Free leap year calculator
Check any year in two seconds. Type a year and the leap year calculator tells you whether it is a leap year, why (the divisible-by-4/100/400 rule), how many days its February has, and the next and previous leap years — updated live, as you type.
On this page14 sections
| Year | Days in Feb | Leap? |
|---|---|---|
| 2016 | 29 | Leap |
| 2020 | 29 | Leap |
| 2024 | 29 | Leap |
| 2028 | 29 | Leap |
| 2032 | 29 | Leap |
| 2036 | 29 | Leap |
Uses the Gregorian calendar rule (divisible by 4, except century years not divisible by 400). See the century exceptions
Results are estimates. Consult a professional.
What is a leap year?
A leap year is a year with 366 days instead of the usual 365 — an extra day, 29 February, is added to the calendar. Leap years happen almost every four years, and this leap year calculator tells you instantly whether any year you enter is one, why, and how many days its February holds.
The extra day exists to keep the calendar in step with the Earth's orbit around the Sun. A common (non-leap) year has 365 days and a 28-day February; a leap year has 366 days and a 29-day February. The rule for deciding which is which is short, but it has a twist for century years that trips most people up — which is the whole reason a calculator is useful.
How to calculate a leap year (the divisible-by-4 rule)
The modern Gregorian calendar decides a leap year with a three-part rule. Work through it in order and the first rule that applies gives the answer:
- Is the year divisible by 4? If no, it is a common year — stop. If yes, continue.
- Is the year divisible by 100? If no, it is a leap year — stop. If yes, continue.
- Is the year divisible by 400? If yes, it is a leap year. If no, it is a common year.
In plain terms: most years divisible by 4 are leap years. The only exceptions are century years — and a century year is a leap year only if it is also divisible by 400. That is why 2000 was a leap year but 1900 was not, even though both divide evenly by 4.
A worked example using the leap year calculator
Priya wants to know whether 2024 is a leap year before booking a trip around the end of February. Here is exactly how the calculator works through the rule.
Step 1 — Divide the year by 4
2024 ÷ 4 = 506 with no remainder, so 2024 passes the first test. A year that fails here (like 2023) would be a common year straight away.
Step 2 — Check whether it is a century year
2024 does not end in 00, so it is not divisible by 100. The century exception does not apply, and the rule stops here: 2024 is a leap year. (The 400 test is only needed for years like 1900 or 2000.)
Step 3 — Read the result
Because 2024 is a leap year, its February has 29 days and the year has 366 days in total. The calculator also surfaces the surrounding leap years: the previous one was 2020 and the next is 2028.
Why do we have leap years?
A leap year exists because the Earth does not orbit the Sun in a tidy whole number of days. One orbit — a tropical year — takes about 365.2422 days (roughly 365 days, 5 hours, 48 minutes, and 45 seconds), not exactly 365.
If the calendar simply used 365 days every year, it would drift by about a quarter of a day annually. After four years that is nearly a full day; after a century it would be about 24 days, and the seasons would slowly slide out of place — eventually spring would arrive in what the calendar called winter. Adding one day every four years absorbs that leftover quarter-day and keeps the calendar locked to the seasons.
The extra day is placed in February — the shortest month — because adding it there causes the least disruption to the rest of the calendar. That is why the leap day is 29 February and not, say, a 32nd of some other month.
Century years: the 100 and 400 exceptions
Adding a leap day every four years is itself slightly too much — it over-corrects by about 3 days every 400 years. The Gregorian calendar fixes this by removing three leap days each four centuries: century years are not leap years unless they are divisible by 400.
| Century year | Divisible by 4? | Divisible by 400? | Leap year? |
|---|---|---|---|
| 1600 | Yes | Yes | Leap |
| 1700 | Yes | No | Common |
| 1800 | Yes | No | Common |
| 1900 | Yes | No | Common |
| 2000 | Yes | Yes | Leap |
| 2100 | Yes | No | Common |
| 2200 | Yes | No | Common |
| 2400 | Yes | Yes | Leap |
Century years are the only place the leap-year rule can surprise you: 1700, 1800, 1900, 2100, 2200, and 2300 are common years; 1600, 2000, and 2400 are leap years.
List of leap years (1900–2100)
Between 1904 and 2096 the pattern is simple — every fourth year is a leap year — because there is no qualifying century year in that stretch (1900 and 2100 are both common years). The table below lists them by decade so you can scan to any year quickly.
| Decade | Leap years |
|---|---|
| 1900s | 1904, 1908 (1900 is NOT a leap year) |
| 1910s–1920s | 1912, 1916, 1920, 1924, 1928 |
| 1930s–1940s | 1932, 1936, 1940, 1944, 1948 |
| 1950s–1960s | 1952, 1956, 1960, 1964, 1968 |
| 1970s–1980s | 1972, 1976, 1980, 1984, 1988 |
| 1990s | 1992, 1996 (2000 IS a leap year) |
| 2000s–2010s | 2000, 2004, 2008, 2012, 2016 |
| 2020s | 2020, 2024, 2028 |
| 2030s–2040s | 2032, 2036, 2040, 2044, 2048 |
| 2090s–2100s | 2092, 2096 (2100 is NOT a leap year) |
Recent leap years follow the every-4-years pattern. The two breaks are 1900 (skipped) and 2100 (skipped); 2000 was included because it divides by 400.
Leap year birthdays (born on February 29)
People born on 29 February are sometimes called "leaplings" or "leap-year babies." Because the date only exists in leap years, a true 29 February birthday lands on the calendar just once every four years — and skips entirely across the century-year gaps like 1900 and 2100.
- Odds of being born on a leap day are about 1 in 1,461 (one leap day among 1,461 days in a four-year cycle), so leaplings are rare.
- In common years, leaplings usually mark their birthday on 28 February or 1 March — there is no single legal standard, and it varies by country and purpose.
- Ageing is normal: a leapling born in 2000 turned 24 in 2024 like everyone else; only the exact-date celebration is intermittent.
To count exact days lived or the years between two dates regardless of leap days, pair this with the days between dates calculator or the date calculator.
Common leap year questions
How many days are in a leap year?
366 days — one more than a common year's 365. The extra day is 29 February, so a leap year's February has 29 days instead of 28.
Is every 4 years a leap year?
Almost. Every year divisible by 4 is a leap year except century years that are not divisible by 400. So 1700, 1800, 1900, 2100, 2200, and 2300 break the every-4-years pattern, while 1600, 2000, and 2400 keep it.
Why was 2000 a leap year but 1900 was not?
Both divide evenly by 4 and by 100, which would normally make a century year a common year. The deciding test is divisibility by 400: 2000 ÷ 400 is exact, so it was a leap year; 1900 ÷ 400 is not, so it was a common year.
How this calculator works and sources
This leap year calculator applies the Gregorian calendar rule exactly: a year is a leap year when it is divisible by 4, unless it is a century year not divisible by 400. The maths is pure integer logic run in your browser — nothing is sent anywhere — and the rule, the ~365.2422-day tropical year, and the 1582 introduction of the Gregorian calendar are standard, well-documented astronomy and calendar facts.
United States Naval Observatory (USNO) — Leap Years and the Gregorian calendar rule.Frequently asked questions about the free leap year calculator
About this leap year calculator
This leap year calculator runs entirely in your browser. The year you type never leaves your device — nothing is sent to a server, logged, or shared. It applies the Gregorian rule exactly: a year is a leap year if divisible by 4, except century years not divisible by 400, updating instantly on every change.
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