Convert Months to Years

About converting Months to Years

Months (mo) and Years (yr) are both units of time, so converting between them is a single multiplication: multiply your Months figure by 0.08333. Ten Months comes to 0.8333 Years, and a hundred works out at 8.3333 Years.

Rule of thumb: going from Months to Years divides, so the figure always shrinks — it takes about 12 Months to make a single Year. If your answer came out bigger, you have the conversion the wrong way round.

What is a Month?

The month is the messiest unit in everyday use. Gregorian months run from 28 to 31 days for reasons that are pure historical accretion rather than design, so there is no true number of seconds in a month at all. This converter uses an averaged month of 2,629,800 seconds — one twelfth of a Julian year, about 30.44 days — and that is a convention, not a definition: the answer here is an average, not a fact. It is worth remembering that a month in a contract or a subscription almost always means a calendar month rather than thirty days, and the difference decides real billing dates.

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.

To put both in perspective: a month is one page of a wall calendar, while a year is one lap of the Earth around the Sun.

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