Pregnancy Weeks to Months Calculator: Which Week Is Which Month
Enter a week of pregnancy to see which month and trimester it is, or a month to see its week range. It uses the standard table your hospital does, because pregnancy months are not tidy four-week blocks.
Convert weeks and months
Pick a direction, enter the number, convert. The strip below shows where that week falls.
Why the months are uneven
A pregnancy is dated in 40 weeks but spoken of in 9 months, and 40 does not divide into 9. So a pregnancy month runs about four and a half weeks, not four — which is why 30 weeks is the seventh month, not seven and a half.
Week to month, at a glance
Weeks 41 and 42 are past the due date and still count as the ninth month.
| Month | Weeks | Trimester |
|---|---|---|
| 1 | 1–4 | First |
| 2 | 5–8 | First |
| 3 | 9–13 | First |
| 4 | 14–17 | Second |
| 5 | 18–22 | Second |
| 6 | 23–27 | Second |
| 7 | 28–31 | Third |
| 8 | 32–35 | Third |
| 9 | 36–40 | Third |
Common questions
How many months is 30 weeks pregnant?
The seventh month. Weeks 28 to 31 are month seven, which is also where the third trimester starts.
Why isn't it just four weeks per month?
Because that would make pregnancy ten months. Forty weeks across nine months averages about four and a half.
Which trimester am I in?
Weeks 1 to 13 are the first, 14 to 27 the second, 28 onwards the third.
My count and the app's differ by a month. Which is right?
Almost always that gap is calendar months against pregnancy months. Go with your clinic's figure, which this table matches.
Is 40 weeks nine months or ten?
Nine. Forty weeks is full term and the end of the ninth month.
Reviewed by
- Nakul Phatak — CEO, theAsianparent India & IndonesiaHead of theAsianparent India; father of one
- Roshni Chugani — Head of Marketing, theAsianparent India & Singapore12 years in the mother-and-baby space; mother of two
Published by: theAsianparent editorial team
