When someone says, “I’m 27 weeks pregnant,” it’s hard to know what that means without doing some quick math. It also doesn’t help that no one is technically pregnant until week three or that 40 weeks is still considered the 9th month of pregnancy – c’mon, we all know it’s ten and feels like a million.
Here’s a quick cheat sheet to calculate what week is when.
You can click on the links to learn more about each week or sign up for the Pregnancy Calendar to get weekly updates delivered to your inbox.
First Trimester
- The first trimester of pregnancy is tricky because pregnancy starts before anyone has ovulated or fertilized an egg. It’s easier to calculate a due date from the first day of a period rather than conception. Even if you know the exact time of sex, you won’t know the exact time of conception because it can vary if sperm is being speedy or taking its time.
- 1 week pregnant This is the first day of your last period.
- 2 weeks pregnant uterine lining building up to prep for ovulation.
- 3 weeks pregnant Sperm and egg have met. (Conception.)
- 4 weeks pregnant Four weeks is one month pregnant.
- 5 weeks pregnant Five weeks is just over one month pregnant.
- 6 weeks pregnant Six weeks is one and a half months pregnant.
- 7 weeks pregnant Seven weeks is one month and three weeks pregnant. (Almost two months.)
- 8 weeks pregnant Eight weeks is two months pregnant.
- 9 weeks pregnant Nine weeks is just over two months pregnant.
- 10 weeks pregnant Ten weeks is two and a half months pregnant.
- 11 weeks pregnant Eleven weeks is two months and three weeks pregnant. (Almost three months.)
- 12 weeks pregnant Twelve weeks is three months pregnant.
- 13 weeks pregnant Thirteen weeks is just over three months pregnant.
Second Trimester
- The second trimester runs from week 14 to week 27. It’s the trimester when morning sickness is likely to subside (or not) and when you start to look cute pregnant vs. “are you sure it’s not twins” pregnant.
- 14 weeks pregnant Fourteen weeks is three months and two weeks pregnant.
- 15 weeks pregnant Fifteen weeks is three months and three weeks pregnant. (Almost four months.)
- 16 weeks pregnant Sixteen weeks is four months pregnant.
- 17 weeks pregnant Seventeen weeks is just over four months pregnant.
- 18 weeks pregnant Eighteen weeks is four and a half months pregnant.
- 19 weeks pregnant Nineteen weeks is four months and three weeks pregnant. (Almost five months.)
- 20 weeks pregnant Twenty weeks is five months pregnant.
- 21 weeks pregnant Twenty-one weeks is just over five months pregnant.
- 22 weeks pregnant Twenty-two weeks is five and a half months pregnant.
- 23 weeks pregnant Twenty-three weeks is five months and three weeks. (Almost six months pregnant.)
- 24 weeks pregnant Twenty-four weeks is six months pregnant.
- 25 weeks pregnant Twenty-five weeks is just over six months pregnant.
- 26 weeks pregnant Twenty-six weeks about six and a half months pregnant.
- 27 weeks pregnant Twenty-seven weeks is 6 months and 3 weeks pregnant. (Almost 7 months.)
Third Trimester
- The third trimester runs from week 28 to week 40. This is the home stretch although it rarely feels like it and those last few weeks of pregnancy can feel like a million years.
- 28 weeks pregnant Twenty-eight weeks is 7 months pregnant.
- 29 weeks pregnant Twenty-nine weeks is just over 7 months pregnant.
- 30 weeks pregnant Thirty weeks is 7 and a half months pregnant.
- 31 weeks pregnant Thirty-one weeks is 7 months and 3 weeks pregnant. (Almost 8 months pregnant.)
- 32 weeks pregnant Thirty-two weeks is 8 months pregnant
- 33 weeks pregnant Thirty-three weeks is just over 8 months pregnant.
- 34 weeks pregnant Thirty-four weeks is 8 and a half months pregnant.
- 35 weeks pregnant Thirty-five weeks is 8 months and three weeks pregnant. (I’d probably say “almost nine months.)
- 36 weeks pregnant Thirty-six weeks is 9 months pregnant. (But you’re still not done. Sorry.)
- 37 weeks pregnant Thirty-seven weeks is just over 9 months pregnant.
- 38 weeks pregnant Thirty-eight weeks is 9 and a half months pregnant.
- 39 weeks pregnant Thirty-nine weeks is 9 months and three weeks pregnant. (Officially full term.)
- 40 weeks pregnant Forty weeks is still considered the 9th month of pregnancy. (Due date.)
- 41 weeks pregnant Forty-one weeks is still considered the 9th month of pregnancy. (One week overdue.)
- 42 weeks pregnant Forty-two weeks is 9 months and two weeks overdue.
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