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    Pregnancy calculator: A week-by-week pregnancy calendar

    Wondering how to calculate your pregnancy in months or figure out how far along you are? Let our pregnancy calculator be your guide.

    Updated 29 September 2023 |
    Published 08 September 2023
    Medically reviewed by Dr. Sara Twogood, Obstetrician and gynecologist, Cedars-Sinai Medical Group, California, US
    Written by Sarah Biddlecombe

    How many weeks pregnant are you?

    Your pregnancy


    Track your pregnancy

    As you track pregnancy, you probably know how many weeks you are, but what about how many months? You might also be curious to know how far along in your pregnancy you are so you know how long it’s likely to be before you get to meet your baby for the first time.

    This is where our pregnancy calculator comes in handy. Keep reading to learn more about how to use it, along with some expert pregnancy advice from Dr. Renita White, obstetrician and gynecologist, Georgia, US.

    • Please note that Flo Health does not collect, process, or store any of the data that you enter while using these tools. All calculations are done exclusively in your browser. Flo Health does not have access to the results. All data will be permanently erased after leaving or closing the page.
    • Our Pregnancy Calculator is based on a 40-week pregnancy. As we cannot know when exactly your baby will be born, the calculator is not 100% accurate.
    • Remember that pregnancy calculators, pregnancy due date calculators, and birth date calculators can help you learn more about your estimated due date and pregnancy time line, but they are not a replacement for medical advice. You should always notify your health care provider that you are pregnant. An ultrasound will be needed to date your pregnancy.

    How to use our pregnancy calculator

    Our pregnancy calculator uses some basic information to figure out how far along you are. All you need to do is input how many weeks and days pregnant you are, and the tool will do the rest.

    Once you enter the data, you will get a personalized overview of your pregnancy in months so far. This will include a percentage of how far along you are, how many months pregnant you are, and which trimester you’re in. You’ll also be able to click through to an in-depth article that will tell you about what’s happening during that specific week of your pregnancy. Plus, if you’d like an idea of when your due date is likely to fall, you can use our due date calculator, too. Additionally, you can check out our implantation calculator to find out when the implantation might have occured. Clever, huh?

    Week-by-week calendar

    Pregnancy is an exciting time filled with lots of change — for both your growing baby and your growing body, so you’ll no doubt have lots of questions. Those questions might include: What developmental milestones happen as the weeks go on? What symptoms can you expect and when? And what things should you be thinking about each step of the way? We’ve spoken to Flo experts to bring you the essential knowledge you need for your pregnancy, week by week. Simply scroll through our carousel below to find your week of pregnancy and learn more.

    What is a trimester?

    First up, let’s go over the basics. What exactly is a trimester? “A trimester represents the three sections of time periods of pregnancy,” explains Dr. White. “These periods represent the 1st, 2nd, and 3rd trimesters [up until you give birth].”

    How many weeks are in each trimester?

    Counting from your last menstrual period, there are 13 complete weeks in the 1st trimester and 14 complete weeks in the 2nd trimester. The amount of weeks in your 3rd trimester will vary depending on when your baby is born, so if you’re wondering how long a pregnancy lasts, there’s no specific answer. Your due date marks 40 weeks of pregnancy (or 9.2 months!), but it’s common for your baby to be born on a different date. In fact, only around 5% of babies are actually born on their due date.

    You might also be wondering why your health care provider is counting your pregnancy in weeks rather than in months or even just trimesters. Over to Dr. White. “Many things can change rapidly in a pregnancy, even week by week,” she explains. “Also, some tests and evaluations are needed at specific weeks of pregnancy. So for more precise management and observation, it is better to evaluate pregnancy by week.”

    Tips on having a healthy pregnancy

    Having a healthy pregnancy not only helps to support your baby as it develops, but it also helps to support your body as it adjusts to all the changes that pregnancy can bring. But what are some essential do’s and don’ts to consider when planning a healthy pregnancy?

    Do have a healthy pregnancy diet

    When it comes to a healthy pregnancy diet, there are a few things to consider. First of all, the usual healthy eating principles are the same in pregnancy as they are at other times — it’s good to eat a balanced diet with lots of fruits, veggies, lean protein, healthy fats, and whole grains. However, there are some foods you need to avoid, including foods made from unpasteurized milk and raw or undercooked meats, because of the risk of bacteria and sickness. You can find out more in our guide to a healthy pregnancy diet.

    Do get the right nutrients

    Alongside a healthy diet, you might also be considering taking a pregnancy supplement to help you get all of the nutrients that both you and your growing baby need. One of the most important nutrients is folic acid. Experts recommend you get 600 micrograms per day during pregnancy; you should be able to get some of this from your diet, and you’ll need to take a daily supplement containing at least 400 micrograms of folic acid. But why? “Folic acid is very important in brain and spine development of the baby,” explains Dr. White. “Most importantly, it is vital for the development of the neural tube. The neural tube is part of the early central nervous system.”

    Other recommended nutrients include:

    • Iron
    • Calcium
    • Choline
    • Vitamin D
    • Omega-3 fatty acids
    • B vitamins
    • Vitamin C

    Always speak to your health care provider before taking any new supplements.

    Do keep exercising

    Pregnant women are advised to do around 150 minutes of moderate-intensity exercise each week. And, if you feel able to, keeping up with a healthy workout routine can have many benefits. “Exercises can help with alleviating common pregnancy-related pains, including back and joint pain,” explains Dr. White. “It can help you maintain a healthy pregnancy weight. It has also been shown to decrease the risk of gestational diabetes and shorten your length of labor.”

    If you were active before your pregnancy, it’s probably a good idea to decrease the intensity of your workouts. If you weren’t active, experts advise that you start slow when it comes to introducing exercise into your pregnancy routine. It’s also a good idea to avoid any contact sports or workouts that involve any risk of falling to help keep your baby safe and protected. It’s always a good idea to ask your doctor any questions you have about exercising safely during pregnancy.

    Don’t smoke, take drugs, or drink alcohol

    “Smoking cigarettes and illicit drug use should absolutely be avoided in pregnancy,” says Dr. White. “It can have a negative impact on a baby’s development as well as the development of the placenta. This can lead to fetal growth restrictions, preterm labor, and placental abruption (where the placenta detaches early before the baby is ready to be born).” 

    She adds that: “Alcohol use also has the potential to impact a baby’s development. Since we don’t know how much alcohol it takes to negatively impact a baby, we recommend avoiding it altogether.”

    Of course, these tips aren’t the only things to consider when planning a healthy pregnancy, but they’re a good place to start. Remember to always chat with your health care provider for tailored advice that’s specific to your own pregnancy. You’ve got this!


    Can you show at 4 weeks pregnant?

    As exciting (and reassuring) as it can be to start showing a baby bump, you’re unlikely to have a pregnancy belly at 4 weeks. You could start showing around 12 weeks pregnant, although every pregnancy (and every pregnant belly) is different, so try not to compare yourself to others. 

    What week does my baby’s sex develop?

    Your baby will have an assigned sex from the moment of conception, when the embryo will have either an XX chromosome (female) or XY chromosome (male). If you opt for noninvasive prenatal testing, those results can also show you the sex of your baby (if you choose to find out, of course!). The testing can be done as early as 10 weeks pregnant, so you could find out by around 12 weeks pregnant.

    Should I still be cramping at 5 weeks pregnant?

    Rest assured that cramping that feels a little like period pain is a perfectly normal symptom to experience at 5 weeks pregnant. However, if the cramps become extremely painful, are accompanied by bleeding, or if you have any concerns, always reach out to your health care provider right away.

    Is 33 weeks safe to deliver?

    Babies born at 33 weeks pregnant are considered to be moderate to late preterm, and they have a good chance of survival. However, they’re likely to need extra care, such as in a neonatal unit. This can sound frightening, but rest assured that only 6% to 7% of babies are born between 32 and 36 weeks.

    Is 7 weeks too early for an ultrasound?

    No, 7 weeks isn’t necessarily too early for an ultrasound. The timing of your first ultrasound will depend on your health care provider, but it could indeed be as early as 7 or 8 weeks pregnant. Other providers might not offer an ultrasound until closer to 12 weeks pregnant.

    What is the last organ to develop in a fetus?

    Good question! All of your baby’s organs will be formed by 12 weeks pregnant, but they’ll continue to develop at various stages throughout your pregnancy. Your baby’s lungs are the last organs to fully develop at around 36 weeks pregnant.


    Ananth, C. V., et al. “Maternal Cigarette Smoking as a Risk Factor for Placental Abruption, Placenta Previa, and Uterine Bleeding in Pregnancy.” American Journal of Epidemiology, vol. 144, no. 9, Nov. 1996, pp. 881–89, doi:10.1093/oxfordjournals.aje.a009022.

    Artal-Mittelmark, Raul. “Stages of Development of the Fetus.” MSD Manual Consumer Version, Sep. 2022,

    “Fetal Development.” Cleveland Clinic, Accessed 30 Aug. 2023.

    Field, David, et al. “Chapter 3, The Late And Moderately Preterm Birth Study.” Towards Reducing Variations in Infant Mortality and Morbidity: A Population-Based Approach. NIHR Journals Library, 2016,

    “Foods to Avoid in Pregnancy.” NHS, Accessed 30 Aug. 2023.

    “Health Tips for Pregnant Women.” National Institute of Diabetes and Digestive and Kidney Diseases, Accessed 30 Aug. 2023.

    “How Your Baby Develops Week to Week.” NHS Inform, 25 Jan. 2023,

    “How Your Fetus Grows during Pregnancy.” The American College of Obstetricians and Gynecologists, Aug. 2020,

    Khambalia, Amina Z., et al. “Predicting Date of Birth and Examining the Best Time to Date a Pregnancy.” International Journal of Gynaecology and Obstetrics, vol. 123, no. 2, Nov. 2013, pp. 105–09, doi: 10.1016/j.ijgo.2013.05.007.

    Khoshnood Shariati, Maryam, et al. “Perinatal Complications Associated with Preterm Deliveries at 24 to 33 Weeks and 6 Days Gestation (2011- 2012): A Hospital-Based Retrospective Study.” Iranian Journal of Reproductive Medicine, vol. 13, no. 11, Nov. 2015, pp. 697–702,

    “NIPT Test.” Cleveland Clinic, Accessed 30 Aug. 2023.

    “Nutrition during Pregnancy.” The American College of Obstetricians and Gynecologists, June 2023,

    “Overdue Pregnancy: What to Do When Baby’s Overdue.” Mayo Clinic, 27 July 2022,

    “Pregnancy Diet: Focus on These Essential Nutrients.” Mayo Clinic, 18 Feb. 2022,

    “Preterm Birth.” World Health Organization, 10 May 2023,

    “Stomach Pain in Pregnancy.” NHS, Accessed 30 Aug. 2023.

    “Substance Use during Pregnancy.” Centers for Disease Control and Prevention, Accessed 30 Aug. 2023.

    “Ultrasound in Pregnancy: What to Expect, Purpose, and Results.” Cleveland Clinic, Accessed 30 Aug. 2023.

    Vij, Sarah. “Can You Choose the Sex of Your Baby?” Cleveland Clinic, 7 July 2023,

    “You and Your Baby at 36 Weeks Pregnant.” NHS, Accessed 30 Aug. 2023.

    Zanotti, Salena. “How to Exercise Safely if You’re Pregnant.” Cleveland Clinic, 23 Nov. 2022,

    “Week 5.” NHS, Accessed 30 Aug. 2023.

    “Week 12.” NHS, Accessed 30 Aug. 2023.

    History of updates

    Current version (29 September 2023)

    Medically reviewed by Dr. Sara Twogood, Obstetrician and gynecologist, Cedars-Sinai Medical Group, California, US
    Written by Sarah Biddlecombe

    Published (08 September 2023)

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