Months to Years Converter
Convert months to years — twelve months to the year. Results update as you type; exact factors shown.
One month (average, 30.4369 days) is 0.0833 year (365.2425 days) — see the exact factor, not a rounded rule of thumb.
How the months to years converter works
Time converts through the second. Minutes, hours, days and weeks are exact multiples. A month is taken as the Gregorian average (30.436875 days) and a year as the Gregorian average (365.2425 days = 31,556,952 s); calendar months and leap years vary from these averages.
The US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common time conversions
| From | To | Units |
|---|---|---|
| 1 mo | 0.0833 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 3 mo | 0.25 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 6 mo | 0.5 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 9 mo | 0.75 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 12 mo | 1 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 18 mo | 1.5 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 24 mo | 2 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 30 mo | 2.5 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 36 mo | 3 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 48 mo | 4 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 60 mo | 5 yr | month (average, 30.4369 days) to year (365.2425 days) |
| 120 mo | 10 yr | month (average, 30.4369 days) to year (365.2425 days) |
Units in this converter and their exact factors
| Unit | Symbol | One unit in seconds |
|---|---|---|
| millisecond | ms | 0.001 second |
| second | s | 1 second |
| minute | min | 60 second |
| hour | h | 3,600 second |
| day | d | 86,400 second |
| week | wk | 604,800 second |
| month (average, 30.4369 days) | mo | 2,629,746 second |
| year (365.2425 days) | yr | 31,556,952 second |
FAQFrequently asked questions about time conversion
How many months in a year?
Twelve.
What is 18 months in years?
1.5 years.
How many months is a 30-year mortgage?
360.
Why does the converter use an average month?
Because calendar months vary from 28 to 31 days; the average of 30.44 days keeps long spans accurate.
What is 60 months?
Five years — a common car-loan term.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.