How Far Along Am I In My Pregnancy? 5 Ways To Calculate It

Ad failed to load

Knowledge is power, they say, and that's never so true as when you're calculating the time you've been pregnant. Whether pregnancy came as a surprise, or your baby was one of mice and men's best laid plans, when the urine test comes back positive, your first thought is likely to be, "How far along am I in my pregnancy?" Due dates matter, and it's important to know that your baby is growing according to schedule.

Experts say there are multiple ways to calculate how far along you are now in your pregnancy, including early ultrasounds, estimations based on later ultrasounds, measuring fundal height (the distance between your pubic bone and the top of your bump) after 20 weeks gestation, and good old fashioned counting back from your last missed period.

First Response's website even offers a calculator which combines the date of your last missed period with your average cycle length to approximate a due date. But how many women know their average cycle length? Who even has a cycle anyone could call "average?" Unless you're planning, who's even sure of the date of their last missed period?

Ad failed to load

According to Dr. Seth Plancher, MD, FACOG, of Garden City Obstetrics and Gynecology, not many women are lucky enough to enjoy a clockwork cycle. For the rest, here are the options for determining how far along you are, from early to late.

Ad failed to load

1With An Early Ultrasound


In an interview with Romper, Plancher explained that the absolute best way to calculate how far along you are is to come in for an early ultrasound as soon as you know you're pregnant. Your doctor can compare the data from that ultrasound with your last menstrual period to arrive at your due date.

However, it's important to note that the earlier you receive your ultrasound, the more accurate it will be. Always test for pregnancy after a late period, and if it comes back positive, be sure to make an appointment right away.

"A lot of doctors — and I hear about this from other patients — won’t do an ultrasound until eight weeks or nine weeks along, and I think exactly the opposite," says Plancher, a strong proponent of early ultrasounds, which is defined as an ultrasound performed before the 8th week. As early as week six, Plancher is able to measure the fetus from crown to rump, which helps him to date it precisely (a fetus grows about a millimeter per day). Plancher explains:

2Calculating From Your Last Menstrual Period


Pregnancies are 40 weeks, but you're actually pregnant for only 38 of them. Why? Because for doctors, the pregnancy clock starts its countdown from the day of you last missed period — the tricky date responsible for the infamous two-week wait.

The absolute best way to date a pregnancy is from the date of conception, but Plancher says that can be hard to track, especially if you have sex often (as you tend to do while trying to conceive).

But the day of a missed menstrual period is also hard to track. I know that my period likes to take her sweet time arrivng some months, while on others, she's way ahead of schedule. If you're the lucky lady with a Swiss cycle, I've got great news: you can figure out how far along you are, simply by counting backwards. Plancher notes:

3With A Late Ultrasound


An early ultrasound confers all kinds of benefits, according to Plancher. Not only can you get an accurate date on the pregnancy, but you can also check for tubal pregnancies and reduce your risk of miscarriage (hearing the heartbeat does wonders).

Unfortunately, not everyone knows they're pregnant so early. What if you're really caught off guard, somewhere in the second trimester, say? "Sometimes pregnant women show up at 15 weeks, and then you have to use an ultrasound — but there’s a wider range of error, and you have to know that," Plancher notes.

According to Plancher, first trimester ultrasounds have about a one week range of error; second trimester ultrasounds have two-week range, and third trimester ultrasounds have an incredible three-week range of error — which is like a month of your pregnancy.

Calculating how far along you are gets harder as gestation progresses because of natural variability in fetal size (how big your baby is), and observer error. Reading and measuring those ultrasounds isn't easy, especially as your baby grows and gets to wiggling.

Ad failed to load

4Measuring The Size Of Your Uterus


When you measure your uterus in pregnancy, you're measuring your fundal height, or the distance from the pubic bone to the highest point on your belly. According to Mayo Clinic, fundal height measurements are most useful after 20 weeks gestation, at which point providers expect the height of your uterus to match the number of weeks you've been pregnant. So if you're been pregnant 22 weeks, you should have a fundal height measurement of 22 centimeters. Neat, huh?

Unfortunately, a host of factors can render fundal measurements less accurate, Mayo Clinic reported, including if you're obese, have fibroids, or are carrying multiples.

Mayo Clinic was careful to note that fundal measurements are generally taken to reassure women and their providers that baby is growing on schedule, and that it's not a particularly accurate method of dating a pregnancy.

5With ClearBlue Easy's Advanced Pregnancy Test With Weeks Estimator


You've already taken one test, but here's a reason to take another. ClearBlue Easy's Advance Pregnancy Test With Weeks Estimator can help you figure out when you got so pregnant all of sudden. However, it will only estimate that you are 1 to 2 weeks, 2 to 3 weeks, or 3 plus weeks pregnant, so you do have to catch it pretty early if you want to learn anything you don't already know.

Remember, if you feel woozy, hungry, fatigured, or have missed your period, you should always take some kind of test — or better yet, visit your doctor.

While catching a pregnancy in the second or third trimester isn't ideal, there's also no reason to feel embarrassed. With all that's at stake, doctors will be more than happy to see you at any point in your pregnancy, and only a doctor deserving of a seriously negative Yelp review will dare to judge. If this happens to you, your doctor will estimate how far along you are in your pregnancy based on a notoriously unreliable late ultrasound and perhaps a fundal height measurement. Because these measures aren't perfectly accurate, you should avoid inductions or scheduled C-sections if possible, to give your baby all the time she needs grow.

Check out Romper's new video series, Romper's Doula Diaries:

Check out the entire Romper's Doula Diaries series and other videos on Facebook and the Bustle app across Apple TV, Roku, and Amazon Fire TV.

Ad failed to load
Must Reads

The Pressure To Worry About The Gap Between Kids Is So Bad For Moms

"Two under two is absolutely crazy," a friend recently told me upon hearing the news that I was expecting a second child. "Why would you do this to yourself? Seriously, why?" However harsh her words, she was only echoing the same feelings I'd been ba…
By Marie Southard Ospina

To Be Honest, I Couldn't Survive Motherhood Without My Job

The decision to work outside the home once you've become a parent can be a complicated one. Some people don't really have a choice, and go back to work because they're either a single parent or can't sustain their family on one income. Some choose to…
By Priscilla Blossom

I Feel Guilty That My Kid’s Dad Is A Better Parent Than Me, & That’s Bullsh*t

I was scared, and he was sure. I was clueless, and he was well-researched. I was making mistakes, and he was picking up the pieces. From the moment I found out I was pregnant until just last night, when I threw my hands up in the air and left the alw…
By Danielle Campoamor

These Millennial Parents Are Taking Gender-Neutral Parenting To An Entirely New Level

A woman on the subway looks at my bulbous shape and asks, “What are you having?” I take a deep breath and throw a glance to my 5-year-old. “I’m having a baby,” I say to the woman. “No, no” the woman says laughing as she pushes further. “Are you havin…
By Madison Young

I’m Registered At Babies “R” Us, & I'm Freaking The Hell Out

Hi. My name is Abi, and I’m registered at Babies “R” Us — and I’m freaking out. This may sound silly, but after being a die-hard Toys “R” Us kid, I was so excited to register at their baby store once my husband and I finally got our big fat positive …
By Abi Berwager Schreier

My Daughter Is Obsessed With Being "Pretty" & I'm Way Past Terrified

Last week, when I picked up my daughter after school, she immediately wanted to know if I liked her hair. "Is it pretty?" she asked. Her hair was pulled up into two ponytails that were intertwined into thick, long braids. A shimmering pink and purple…
By Dina Leygerman

7 Things No One Tells You About Having A Baby In Your 20s, But I Will

I was 24 when I found out I was pregnant with my daughter. The pregnancy was a surprise, since I was on birth control (side note: antibiotics and birth control don't mix), but my partner and I decided to continue with the pregnancy and committed to m…
By Candace Ganger

Women Who Miscarry Early Deserve To Grieve — Here's How Hospitals Should Be Helping

When I lost my baby back in 2013, it was because of a very early miscarriage. Because of the little amount of time I spent being pregnant, it was though my child had never really existed, which made the next few years hard — I felt like they had been…
By Risa Kerslake

7 Things I Wish My Partner Had Said To Me In The First Hour After Giving Birth

I don't know if it was the buzz of the surrounding machines, the non-existent cry of our son as the doctors tried to resuscitate him, or the fact that I'd already been through labor and delivery once before, but I knew something was missing after I h…
By Candace Ganger

Moms’ Groups Weren’t For Me, Sorry

I go to my moms’ club everyday of the week, but not usually on weekends. My moms' group is a place I can always count on finding fellow mothers who understand the daily struggles and triumphs of parenthood and of juggling life’s responsibilities. Dep…
By Samantha Taylor

Millennial Women Are Getting Married Later Than Gen X, & The Reasons Why Are Pretty Badass

The battle of the generations seems to come up when it comes to every lifestyle or career choice people make. Women, especially, are an important demographic when it comes to analysts looking at the lifestyle choices we make or the expected milestone…
By Josie Rhodes Cook

I've Had 3 Miscarriages But *Please* Keep Telling Me About Your Pregnancy

I can feel the tension the moment my friend announces her pregnancy. I can hear the forced nonchalant attitude she's willing herself to exude as she fishes for the ultrasound. I know why I was the last to learn that she was expecting; why she keeps l…
By Danielle Campoamor

7 Early Signs You're Going To Need An Epidural, According To Experts

Even if you've constructed an elaborate birth plan, it's impossible to control every aspect of labor and delivery. Complications can occur, proactive measures might be necessary, and your mind is subject to change when those damn contractions really …
By Candace Ganger

I'm Pregnant & I Refuse To Read Any Parenting Books

I didn't read any parenting books when I was expecting my daughter, and I refuse to read any parenting books as I await my second child now. I'm the first to admit that I don't really know what I'm doing when it comes to raising my daughter. A good d…
By Marie Southard Ospina

7 Reasons Why March Babies Are Total Badasses

From the moment you become pregnant, you begin to wonder what your little one will be like. Will they look like you, your partner, or your Great Aunt Edna? Will they be the quiet, thoughtful type or arrive on this planet raring to go? It's fun to ima…
By Caroline Shannon-Karasik

12 Overnight Face Masks To Use To Wake Up Feeling Pampered AF

Spring is right around the corner, and as far as I'm concerned, the sunshine and warm breezes can't come soon enough. But now that we're about to say goodbye to winter, it's a good time to take stock of your facial skincare routine. You know, in the …
By Katie Malczyk

11 Essential Products To Pack In Your Hospital Bag, According To OB-GYNs

The minute you go into labor (or think you're going into labor), chaos ensues. You and your partner are likely to get a little frantic, just like in the movies, so you most definitely want to have a hospital bag packed before the day comes. This prec…
By Abi Berwager Schreier

7 Photos You *Must* Take In The First 6 Months Of Motherhood

In my experience, becoming a mom is like becoming an amateur photographer. There's just something about the need to capture every single coo and sorta-smile that leaves you obsessed with all things photography. I know I couldn't stop taking selfies w…
By Candace Ganger

Here's How Early An Ultrasound Can Actually Determine Your Baby's Sex

From the moment you see those two lines on a pregnancy test, there are a few markers along the way that stand out as especially exciting. Amongst them are hearing your baby's heartbeat and feeling that first, sweet little kick. And if you are finding…
By Caroline Shannon-Karasik

9 Easy Kid Foods To Turn Green, Just In Time For St. Patrick's Day

The best part about having kids is that you get your own personal crew to celebrate the holidays with, in all your color coordinating and matching glory. And with St. Patrick’s Day right around the corner, you are obviously working on turning everyth…
By Mishal Ali Zafar