Convert Years to Seconds

About converting Years to Seconds

Years (yr) and Seconds (s) are both units of time, so converting between them is a single multiplication: multiply your Years figure by 31,557,600. Ten Years comes to 315,576,000 Seconds, and a hundred works out at 3,155,760,000 Seconds.

Rule of thumb: going from Years to Seconds multiplies, so the figure always grows — one Year is already 31,557,600 Seconds. If your answer came out smaller, you have the conversion the wrong way round.

What is a Year?

There is no single year. A Julian year is exactly 365.25 days; a Gregorian calendar year averages 365.2425 days, because its leap rule drops three leap days every four centuries; and the tropical year — the actual round trip of the seasons — is about 365.2422 days. The leap-year rules exist precisely to stop the calendar drifting away from that tropical figure. This converter uses the Julian year of 31,557,600 seconds, the convention astronomers use and the one the light-year is built on, but it is a chosen convention rather than a fact about the Earth.

What is a Second?

The second is the SI base unit of time and the reference every other unit here is measured against. It was originally 1/86,400 of a mean solar day, but the Earth’s rotation is not steady enough to serve as a clock, so since 1967 the second has been defined by the caesium-133 atom: 9,192,631,770 periods of a specific hyperfine transition. Atomic time and Earth time therefore drift apart, which is why leap seconds are occasionally inserted to realign them — a fiddly practice that in 2022 was agreed to be phased out by 2035.

To put both in perspective: a year is one lap of the Earth around the Sun, while a human heartbeat takes about a second.

The converter above updates as you type, and the table lists common values for quick reference. Need the opposite direction? Use the Seconds to Years converter, or browse all Time converters.