Being pregnant

How many weeks pregnant am I?

Calculating your baby's due date isn’t as easy as you might think. Here’s how to figure out how many weeks pregnant you are.

OK, ‘How many weeks pregnant am I’ may seem like a funny thing to ask Dr. Google, but it’s pretty common to be a little confused about your due date—or how many weeks pregnant you are—in the earliest stages of pregnancy. That’s true even if you’ve been tracking your cycles religiously, and even if you suspect you know the exact date of conception.

Here’s why: Pregnancy (which is an average of 40 weeks long) is actually measured from the first day of your last menstrual period—before you’ve finished bleeding, before you’ve ovulated and (often) before you’ve engaged in any, um, baby-making activity.

Many women don’t even bother taking a pregnancy test until they’ve ovulated, had sex, and missed a period. Home pregnancy tests will not work until you’re at least 5-6 days away from the expected date of your next period, anyway. (They measure the accumulation of human chorionic gonadotropin hormone, or HCG, in your urine.)

Because most women’s menstrual cycles are around 28 days or four weeks long, some couples who are trying to conceive refer to the time between ovulation and being able to take a pregnancy test as the “two week wait”—or “TWW,” in message-board acronyms.

Here’s an example: if you just got a positive result on a home pregnancy test and suspect you likely ovulated and conceived about two weeks ago, your medical providers already consider you to be four weeks pregnant.

If you saw a plus sign or double lines on a pee stick (or sticks!) at home, and it still doesn’t feel real to you, know that chances are, you probably really are pregnant. (Congratulations!) The likelihood of false positives on home tests are slim to none. Your family doctor or primary care provider will soon order a blood test to confirm the pregnancy, but most women start with the drug-store home tests.

Depending on how regular or irregular your cycle is, your doctor or midwife might also schedule you for a dating ultrasound to measure the developing embryo and calculate your due date more precisely. (Read more about dating ultrasounds in our week-by-week pregnancy articles here.) The earlier the dating ultrasound is conducted, the more accurate it is. (Care providers usually aim to get it done between week 6 and week 11 of pregnancy.) If the embryo is still quite small, the ultrasound tech may use a transvaginal wand to do an internal pelvic ultrasound, in addition to the more common gel-on-abdomen ultrasound method.

If you have a fairly predictable cycle, our online due date calculator can probably tell you what date you’ll spend the next nine months counting down to. And, just for fun, you can start speculating about your little one’s likely astrological sign, too.

Read more:
What does a faint line on a pregnancy test mean?
Implantation bleeding: signs, symptoms and what it means