Months to weeks
Multiply months by 4.3482 to get weeks.
9 mo = 39.1339 wk
How to convert months to weeks
The week is exactly 7 days. The month is about 30.44 days on average — a twelfth of a 365.25-day year, not a calendar month (which runs 28 to 31 days).
Worked example — 9 mo: 9 × 4.3482 = 39.1339 wk.
Months to weeks table
| Months | Weeks |
|---|---|
| 1 mo | 4.3482 wk |
| 2 mo | 8.6964 wk |
| 3 mo | 13.0446 wk |
| 6 mo | 26.0893 wk |
| 9 mo | 39.1339 wk |
| 12 mo | 52.1786 wk |
| 18 mo | 78.2679 wk |
| 24 mo | 104.3571 wk |
| 36 mo | 156.5357 wk |
Reverse and related
About months and weeks
Month (mo)
1 mo = 4.3482 wkDefinition. About 30.44 days on average — a twelfth of a 365.25-day year, not a calendar month (which runs 28 to 31 days)
History and origin
The month began as the period of the lunar phases, about 29.5 days, but calendar months were fixed at 28 to 31 days to fit twelve into a year. For conversions an average month is taken as a twelfth of a year, about 30.44 days.
Current use
Months organise the calendar, billing cycles and subscriptions, and count durations such as pregnancies and projects.
Source: IAU/ISO 80000-3 Julian year: 1 a = 365.25 d exactly, a convention for expressing durations. The average month here is that year divided by 12. Neither is an SI unit.
Week (wk)
1 wk = 0.229979 moDefinition. Exactly 7 days
History and origin
The week is a seven-day cycle with ancient roots in Babylonian and Jewish tradition, tied to the seven classical planets and to religious observance. Unlike other time units it has no astronomical basis.
Current use
Weeks organise schedules and are used to count the length of pregnancies and projects.
Source: BIPM SI Brochure (2019); the second is defined by the caesium-133 transition
Where people use this
Months: durations, billing and subscriptions. Weeks: schedules, pregnancy and projects. A month is about 4.35 weeks.
Every value is carried to full double precision; the display is rounded.
Sources: BIPM SI Brochure (2019); the second is defined by the caesium-133 transition; IAU/ISO 80000-3 Julian year: 1 a = 365.25 d exactly, a convention for expressing durations. The average month here is that year divided by 12. Neither is an SI unit..
Questions people ask
How many weeks in a month?
A month is about 4.35 weeks on average.
How many weeks is 3 months?
3 months is about 13 weeks.
How many weeks is 9 months?
9 months is about 39.1 weeks.