Everyone says pregnancy lasts nine months, but your provider talks in weeks — and turning one into the other is less obvious than it looks. Forty weeks doesn’t divide neatly into nine, so “6 months pregnant” is a range of weeks rather than a single number, and different charts draw the lines slightly differently. This guide gives you the full months-to-weeks conversion, explains where the numbers come from, and shows how to convert your own dates.
The quick chart: months to weeks
The table below uses the most common obstetric convention, the same one behind our weeks-to-months converter. Months are uneven buckets of four or five weeks so that the full 40 weeks lands at the end of month nine.
| Month | Weeks | Trimester | Where you are |
|---|---|---|---|
| Month 1 | Weeks 1–4 | First | Ovulation, conception and implantation; a test may just turn positive |
| Month 2 | Weeks 5–8 | First | Missed period, early symptoms, first heartbeat on scan |
| Month 3 | Weeks 9–13 | First | Embryo becomes a fetus; dating and nuchal scans; end of first trimester |
| Month 4 | Weeks 14–17 | Second | Second trimester begins; energy often returns |
| Month 5 | Weeks 18–22 | Second | Halfway point; anatomy scan; first flutters of movement |
| Month 6 | Weeks 23–27 | Second | Viability milestone (24 weeks); glucose screening; end of second trimester |
| Month 7 | Weeks 28–31 | Third | Third trimester begins; kicks get stronger |
| Month 8 | Weeks 32–35 | Third | Baby usually turns head-down; rapid weight gain |
| Month 9 | Weeks 36–40 | Third | Early term at 37, full term at 39, due date at 40 |
If you know your week already, jump straight to the matching page — for example 20 weeks pregnant in months or 27 weeks pregnant in months — for a day-by-day breakdown of that week.
Why 40 weeks isn’t exactly 9 months
Pregnancy is counted from the first day of your last menstrual period and a full-term pregnancy is 40 weeks, or 280 days. Nine calendar months, meanwhile, average about 39 weeks (273–275 days). So pregnancy is really “nine months and a week” — long enough that people sometimes joke it is closer to ten lunar months of 28 days each, which is exactly what 280 days works out to.
That extra week is the root of every months-to-weeks disagreement. There are three ways people commonly handle it:
- Uneven buckets (the chart above). Months alternate between four and five weeks so month nine ends at week 40. This is what most week-by-week apps and pregnancy books use, and it is the convention we use across the site.
- Even division. Divide 40 weeks by 9 and each month is about 4.4 weeks: month one is weeks 1–4, month six is weeks 23–26, month nine is weeks 36–40. Almost the same, but a week can land in a different month near the boundaries.
- Calendar months. Count actual months forward from your last period. Because months are 28–31 days long, “six months pregnant” by this method is about 26 weeks.
None of these is more correct than the others — there is no medical standard for months, only for weeks. That is why your provider, your scan reports and your maternity notes all use weeks and days (like “26+3”). If precision matters, use weeks.
Month-by-month conversion, in plain words
- 1 month pregnant = about 4 weeks. For most of month one you aren’t technically pregnant yet — weeks one and two cover your period and ovulation, and conception happens around the end of week two. A sensitive test may show a faint line by the end of week four.
- 2 months pregnant = 5 to 8 weeks. Your period is late, hCG is climbing quickly, and nausea and fatigue often peak toward the end of this month.
- 3 months pregnant = 9 to 13 weeks. By 12 weeks the risk of miscarriage has fallen sharply, which is why many people share their news at the three-month mark.
- 4 months pregnant = 14 to 17 weeks. The second trimester starts at 14 weeks 0 days. Many people feel their most energetic here.
- 5 months pregnant = 18 to 22 weeks. Twenty weeks is the halfway point, and the anatomy scan (usually 18–22 weeks) can often reveal the baby’s sex if you want to know.
- 6 months pregnant = 23 to 27 weeks. Twenty-four weeks is the point from which babies born early have a chance of survival with intensive care, and glucose screening for gestational diabetes is typically done between 24 and 28 weeks.
- 7 months pregnant = 28 to 31 weeks. The third trimester begins. Providers often suggest starting to notice daily movement patterns from 28 weeks.
- 8 months pregnant = 32 to 35 weeks. Most babies settle head-down, and weight gain is at its fastest.
- 9 months pregnant = 36 to 40 weeks. Early term starts at 37 weeks 0 days, full term at 39 weeks 0 days, and your due date is 40 weeks 0 days. Weeks 41 and 42 are late term and post-term — still “nine months,” just past the estimated date.
How to convert your own dates
- Find your week. Count from the first day of your last period to today, or let the pregnancy week calculator do it. If an early ultrasound gave you a different due date, use the scan dates — they are more accurate than period dates.
- Look up the week in the chart above to get your month and trimester.
- Going the other way? If someone tells you they are “six months,” assume roughly 23–27 weeks — and if it matters (booking a flight, planning maternity leave), ask for the week.
A quick sanity check that helps a lot of people: month number ≈ weeks ÷ 4.4, rounded up. Twenty-six weeks ÷ 4.4 = 5.9, so month six. Thirty-three ÷ 4.4 = 7.5, so month eight. It won’t be perfect at the boundaries, but it is never more than a month out.
Weeks vs. months vs. trimesters
Trimesters are the third way of slicing pregnancy, and they don’t line up cleanly with months either. The first trimester runs to 13 weeks 6 days (roughly months one to three), the second from 14 weeks to 27 weeks 6 days (months four to six), and the third from 28 weeks to birth (months seven to nine). So “end of the second trimester” and “end of month six” mean the same thing, but “end of the first trimester” is week 13, not week 12 — a common source of confusion.
The bottom line
Pregnancy is 40 weeks, which is nine months and a little bit. Using the standard convention, three months is weeks 9–13, six months is weeks 23–27, and nine months is weeks 36–40 — but every month spans four or five weeks, so a month can only ever be a range. When you need an exact figure, count in weeks and days the way your provider does, and use the weeks-to-months converter whenever you need to translate back for friends and family.