Years to Months
An instant years-to-months converter, with the formula and a reference table below.
| Years | Months |
|---|---|
| 1 yr | 12 mo |
| 2 yr | 24 mo |
| 3 yr | 36 mo |
| 5 yr | 60 mo |
| 10 yr | 120 mo |
| 25 yr | 300 mo |
| 50 yr | 600 mo |
| 100 yr | 1200 mo |
How to use
- Enter a value in the Years field.
- The Months figure appears immediately — no button to press.
- Typing in the Months field converts back to Years the same way.
- Use the reference table for the values that come up most often.
Years to Months formula
To convert years to months, multiply by 12.
mo = yr × 12
Put another way, one year is exactly 12 months.
Why this factor: the year and the month are both defined against the second, so dividing one definition by the other gives 12 directly. Both definitions are set out in full below.
To go the other way, divide by 12 — or use the Months to Years converter, which is the same calculation reversed.
Worked example
Take 90 yr and multiply by the factor 12: the result is 1080 mo.
90 yr × 12 = 1080 mo
The converter above does this for any value you type, in either direction.
What is a year?
A year here means the Julian year, the fixed-length year used for scientific and financial arithmetic.
Definition: Exactly 365.25 days, so exactly 31,557,600 seconds.
Where it is used: Astronomy (the light-year is built on it), interest and depreciation calculations, and age arithmetic.
Worth knowing: The Gregorian calendar year averages 365.2425 days, so the two diverge by about 11 minutes per year.
What is a month?
A month here means the *average* calendar month, since real months vary from 28 to 31 days.
Definition: Taken as one twelfth of a Julian year — 30.4375 days, or exactly 2,629,800 seconds.
Where it is used: Subscription and loan periods, rent, and any calculation that needs a consistent month length.
Worth knowing: Because calendar months differ in length, this average is the right choice for arithmetic but will not match a specific month exactly.
Years vs Months
The year and the month belong to the same family of units, so converting between them is usually a matter of shifting a decimal point or applying a small whole-number factor.
Frequently asked questions
How many months are in a year?
One year equals 12 months.
What is the formula to convert years to months?
Multiply the number of years by 12. To reverse it, divide by 12 instead.
How do I convert months back to years?
Divide by 12, which is the same as multiplying by 0.0833333333.
How many months are in 10 years?
10 yr works out to 120 mo.
Is there anything to watch out for with years?
The Gregorian calendar year averages 365.2425 days, so the two diverge by about 11 minutes per year.
How is the year defined?
Exactly 365.25 days, so exactly 31,557,600 seconds.