On the forums I frequent, there are always new moms asking “If I’m x weeks pregnant, how many months am I?” or “What trimester is x weeks?”  Here is the tried-and-true reference calendar for pregnancy that I use.

First Trimester

Month 1: Weeks 1-4

Month 2: Weeks 5-8

Month 3: Weeks 9-13

Second Trimester

Month 4: Weeks 14-17

Month 5: Weeks 18-21

Month 6: Weeks 22-26

Third Trimester

Month 7: Weeks 27-30

Month 8: Weeks 31-35

Month 9: Weeks 36-40+