6 months pregnant how many weeks is that?

Depends: depends on whether you're in the beginning of the month, mid month or end. Somewhere between 24 and 28 weeks. There are many due date calculators online that can tell you the number of weeks and days you are. Try them.

No exact answer: Since months are more approximate than weeks we can only give a range. Also, the tendency is to equate 4 weeks to a month but that is not quite accurate. Think of the day exactly 3 months from your due date when you are definitely 6 months. You have 13 weeks to go, so you are 27 weeks of a 40 week pregnancy. Plus or minus 2 weeks gives a range of 25 to 29 weeks when you are "6 months"