Doctors count pregnancy in weeks, but everyone asks in months — and because months aren’t all four weeks long, the conversion is messier than it looks. Set your week below to see which month and trimester you’re in, how far along you are, and how the full 40 weeks map onto nine months.
A calendar month averages about 4.35 weeks, not 4 — so 40 weeks of pregnancy is roughly 9¼ calendar months, not 10. That’s why a simple “divide by four” puts you a month ahead of where you really are. The mapping used here follows the common obstetric convention: months 1–3 cover weeks 1–13 (first trimester), months 4–6 cover weeks 14–27 (second), and months 7–9 cover weeks 28–40 (third).
Keep in mind that clinicians will always talk in weeks and days ("24 and 3") because a month is too blunt an instrument — babies change enormously within a single month. Use months for family and friends, weeks for your doctor, and this page whenever the two need translating.