An easy way to find the number of weeks in a month is to start with finding out how many days are in that month. You can find the number of days in a month by looking at a calendar app, a physical calendar or a Web-based calendar. Then, you can use a unit converter app to convert days to weeks. Google's unit converter is one of many Web-based unit converters that you can use.
There are between 28 and 31 days in each of the 12 months; therefore, each month has at least four weeks. No matter what month you are referring to -- whether it's February or December -- there are between four and 4.42857 weeks in a month. If you want to find the exact number of weeks in each month, you can start by looking at the calendar and recording the number of days in a particular month. For example, February is the only month with either 28 days in common years or 29 days in leap years. Since there are seven days in a week, 28 days is exactly 4 weeks long; 29 days is 4.14286 weeks. Every other month is either 30 or 31 days long; 30 days is 4.28571 weeks and 31 days is 4.42857 weeks.