- 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 Due Date Calculator is based on a 28-day cycle (cycles can vary from 20 to 45 days), and your period and ovulation are considered to be the first 2 weeks of pregnancy. As this method is affected by the regularity of your menstrual cycle, the due date predictor is not 100% accurate.
- Remember that pregnancy due date calculators, birth date calculators, and pregnancy calculators can help you learn more about your estimated due date and pregnancy timeline, but they are not a replacement for medical advice. You should always notify your health care provider that you are pregnant. Sometimes an ultrasound will be needed to date your pregnancy.
Gestational age is the age of pregnancy and is counted from the first day of your LMP. So technically it includes two weeks during which you weren't pregnant yet.
Week 4
At 4 weeks pregnant, your future baby has finally found his home for the next eight months. The blastocyst has arrived from a fallopian tube to your uterus. You can get a positive pregnancy test result at this stage.
Week 5
By week 5, you should have missed your period, which is one of the most obvious sign you're expecting. Under the influence of hormonal changes, you can feel the first signs of pregnancy: breast swelling, fatigue, headache, and back pain.
Week 6
Starting from pregnancy week 6, you may experience morning sickness. This is the result of hormonal changes occurring in your body. Malaise, breast swelling, darkening of the nipple areola, and frequent urination can bother you, too. In case of bleeding, you should consult your doctor.
Week 7
At 7 weeks pregnant, symptoms start kicking in and your uterus almost doubles in size. Be prepared for a possible increase in nausea, fatigue, heartburn, and other pregnancy symptoms. Morning sickness may give a lot of trouble. Try to find some ways to cope with it.
Week 8
At 8 weeks pregnant, you need to plan your first visit to the gynecologist. The doctor will prescribe the necessary tests and examinations for the first trimester of pregnancy. You may feel the growing discomfort of morning sickness. Try to be patient; it usually lasts until the 14th week only.
Week 9
At 9 weeks pregnant, your baby is already about 0.6–0.7 in (16–18 mm) and weighs about 0.11 oz (3 g). The tail has disappeared; human features are becoming more distinct. The joints of his/her hands and legs can flex; the nipples and hair follicles are developing. Taste buds are beginning to form on the tongue, as well as primary tooth buds in the gums.
Week 10
Week 10 of pregnancy is the time when almost all vital organs and tissues of your baby have formed. Now, they are beginning to function and grow rapidly. He or she can swallow amniotic fluid and move their arms and legs. The skin is getting covered with small hair and the fingers have tiny nails. Testes in boys already start to produce testosterone.
Week 11
At 11 weeks pregnant, your baby has already reached 2 in (5 cm) in size. Now, his/her head is half the length of the body, but in the coming weeks, the body will grow enough to make up for it. The fetus skin is so thin and translucent that through it you can see an extensive network of vessels. Placental vessels are expanding to provide the fetus with necessary nutrients and oxygen.
Week 12
At 12 weeks pregnant, your baby weighs about 0.49 oz (14 g). His/her vocal cords are forming, and kidneys are starting to produce urine, filling the bladder. Although you cannot feel it yet, you can see the baby during a sonogram screening (ultrasound).
Week 13
Welcome to the last week of the first trimester! Most early pregnancy symptoms will soon be left behind. At 13 weeks pregnant, your baby is constantly growing. Now, he/she is more than 2.8 in (7 cm) from the top of his/her head to the coccyx.
Week 14
At 14 weeks pregnant, your baby is developing rapidly. In a while, you will be able to feel them moving and kicking. Your body starts actively gaining weight. This occurs due to an increase in blood and lymph volume.
Week 15
At 15 weeks pregnant, your baby your baby is actively drawing in amniotic fluid through his/her nose. Very soon you'll start looking pregnant indeed as your uterus has risen from your pelvic region to your lower abdomen. Time to plan pregnancy shopping!
Week 16
You’re on week 16 of your pregnancy, and things are really starting to gear up! Your tiny baby is not so tiny anymore, and it most definitely looks like a human baby now. By week 16 of your pregnancy, you’re 4 months in. That means you’re nearly halfway there and only have 5 more months to go!
Week 17
If you’ve been enjoying a relatively subtle pregnancy with very little belly to show for it, that’s probably over now! Your waist will gradually disappear as your uterus moves upwards and out of your pelvis.
Week 18
If you’ve been astonished by your baby’s rapid growth and weight gain over the last few weeks, by week 18 this will start to level off a little — but there’s still lots of big news in your little one’s early life! At this stage, he or she can yawn, stretch, and even make facial expressions like frowning. The baby’s sense of taste is developing, and taste buds can now distinguish between sweet and bitter.
Week 19
At 19 weeks pregnant, your rounded belly is very noticeable. The first hair appears on the baby's head, and the brain areas responsible for the senses — tactile, gustatory, olfactory, visual and auditory — are developing rapidly.
Week 20
Congratulations! You are halfway to meeting your baby. The baby's legs have almost straightened, so from now on, he/she will be measured from head to toe.
Week 21
As a 21 week pregnant woman, you have crossed the halfway line on your journey to becoming a mother. Your baby is getting bigger. You can now definitely feel her presence as she explores the real estate that you’ve prepared for her.
Week 22
If you are entering the 22nd week of your pregnancy, without doubts it is getting crowded in there! Your baby is growing and invading your space. And your uterus stretches to about 2 cm (0.8 in) above your belly button to fit your growing baby.
Week 23
For many women, being 23 weeks pregnant is an exciting time because you may finally be showing your baby bump! Among other things, your baby’s eyes and lips are taking shape. They will begin to gain weight more weight which will eventually fill out their wrinkly skin.
Week 24
At 24 weeks pregnant, your baby is almost a foot long. You could be experiencing a tingling sensation in your joints, which is known as carpal tunnel syndrome. It is a common condition during pregnancy which occurs due to fluid build-up in your joints which results in compression of the median nerve.
Week 25
Once you reach week 25 of your pregnancy, you’ll be nearing the end of your second trimester. It can feel like times flies! At 25 weeks pregnant, you’re approximately 5 months and 2 weeks along. Your baby has been growing steadily and even though it’s still not ready, it won’t be long before it comes into the world.
Week 26
You’re likely to put on between 16 and 22 pounds by now. At one point during this week, your baby will open his or her eyes for the first time. He or she is not yet able to see anything inside of the uterus but will blink closing and opening his or her eyes when falling asleep and waking up.
Week 27
The 27th week of the pregnancy marks the final two weeks of the second trimester. If your baby is more active at night you might suffer from insomnia and have trouble sleeping. Compensate for the lack of sleep time during the night by napping during the day more when the baby is sleeping.
Week 28
At 28 weeks you are now entering the third trimester of your pregnancy. At this stage, your baby is pretty well-developed. Her organs, tissues, and nerves continue to grow, but she already has all of the systems necessary for survival outside the uterus. Towards the end of the pregnancy, babies start to recognize familiar sounds and voices.
Week 29
At 29 weeks pregnant, you're likely to develop varicose veins like 40 percent of expectant moms. It's also a good time to start doing a kick count. Let your doctor or midwife know if you notice that your baby is becoming less active.
Week 30
At 30 weeks pregnant, you are likely to experience shortness of breath. Your baby is still up high near your rib and is waiting a bit – it is soon expected to drop down into your pelvis.
Week 31
At 31 weeks pregnant, your breasts can get leaky producing the first baby’s food – colostrum. This is one of the symptoms that your body is getting ready for the big day. You are likely to experience shortness of breath. This week your baby is going through major nerve and brain development.
Week 32
At 32 weeks pregnant, your body may start flexing its muscles preparing for the big day. Your baby is also preparing for her debut mastering the skills she’ll need to thrive outside your womb: swallowing, breathing, sucking.
Week 33
At 33 weeks pregnant, you may notice that your baby’s movements are affected by your daily routine. Your belly continues to grow and it’s getting even more troublesome to find a comfortable sitting or sleeping position.
Week 34
At 34 weeks pregnant, your breasts could start leaking small amounts of yellowish colostrum. Your baby is already the size of a school bag and weighs as a melon. If you’re worried about your safety at work, time to talk to your employer about maternity benefits.
Week 35
At 35 weeks pregnant, you may know how your baby’s moving in your womb just by looking at your bump. It can you give you some discomfort and make you a bit breathless. At this point, many moms can’t wait for the baby to get here, while others are feeling a bit anxious about giving birth. Both feelings are completely normal!
Week 36
At 36 weeks pregnant, your baby is sleeping between 60 and 80% of the time. It has finally moved into your pelvic cavity, the pressure on your diaphragm is released, and lightening happens. Your baby can now open its eyes, suck its thumb, breathe, and recognize voices!
Week 37
Welcome to your 37th week of pregnancy, and congratulations! The baby moves further into the pelvis. It is considered to be ‘at-term’ and can actually arrive any day now. Make sure you are ready for the arrival of a new family member.
Week 38
At 38 weeks pregnant, you can find yourself spending the whole life peeing. The pressure on your bladder is tremendous. Your baby is a fully functioning little human and your placenta is fully grown.
Week 39
Welcome to the week 39 of pregnancy! Your baby is full term, meaning that it is fully developed and is only waiting for the right time to make an entrance into the world. Have you prepared everything that is needed to welcome your baby?
Week 40
At 40 weeks pregnant, you may feel disappointed that your due date has come and gone. Don’t panic and make the last preparations for a new human who’ll soon join the world.
Week 41
At week 41 of pregnancy, you might be dying out of the desire to give birth and see your baby. But rest assured that plenty of moms-to-be go past their due date and everything turns out just fine.
Week 42
When a pregnancy lasts for 42 weeks or more it is referred to as a post-term pregnancy. While not many studies exist that prove why some women’s pregnancy lasts for 42 weeks, medical experts believe that factors such as hormones, genetics, and even obesity can be the cause.
If you’ve taken a pregnancy test and it appears to be positive, you might be wondering what happens next. That’s where our Due Date Calculator or due date predictor comes in.
By using some basic information about your last period and cycle length, our pregnancy calculator can help you work out your estimated due date (EDD — aka when you might meet your baby). This information is also useful if you’re thinking about the baby’s due date timings before you start trying to conceive.
Try using our Due Date Calculator now and then scroll down for more on how due dates (and pregnancy) are calculated, plus information on when you could have conceived and how far along you might be.
When is my due date? How is due date calculated?
Lots of us assume that a pregnancy is exactly 9 months long, but that’s not the case.
“The 9 months of a pregnancy are actually 40 weeks,” Dr. Charlsie Celestine, Flo board member, obstetrician, and gynecologist (OB-GYN), explains. “The due date is 40 weeks from the first day of your last menstrual period (LMP). But some women can go beyond that to 41 weeks.”
In fact, the first thing you’ll likely notice when you let your health care provider know you are pregnant is that pregnancy is calculated in weeks rather than months — and your baby’s estimated due date falls on the 40th week, when you’ll actually be around 10 months pregnant.
That’s to account for the fact that pregnancy is counted from your LMP, not the date you conceived, so 2 extra weeks are added even though you weren’t pregnant. Also, this method recognizes that not all months have the same number of days, so you’ll likely still be pregnant at 9 months.
You might also see figures like 13/5 or 13+5 in your notes. Pregnancy is counted in complete weeks, so 13/5, 13+5, or a variation of this would mean you’re 13 weeks and 5 days pregnant. Learn more about how you count pregnancy weeks here.
Why is working out your due date so important? Dr. Celestine says there’s a number of reasons doctors estimate a baby’s due date. “There are certain tests that need to be performed at certain gestational ages during a pregnancy,” she explains. “Knowing how far along you are is also important for following the growth of the baby, when we can expect to deliver, and much, much more.”
Your health care provider will usually calculate your due date based on one or a combination of the following methods, so let’s find out more about how they work.
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How to calculate due date: First day of last period
As we now know, the most commonly used method is to count “40 weeks from the first day of your LMP," Dr. Celestine says. Your health care provider will usually work out your due date using your LMP info at your first appointment.
“You calculate [EDD] using the first day of the last menstrual period [adding exactly 1 year to it], add 7 days to that, and then subtract 3 months (Naegele’s rule). More commonly though, I use a pregnancy wheel using the first day of the menses [period].”
A pregnancy wheel or gestation calculator is a simple calendar that works out your due date or baby’s birth date based on different inputs, such as your LMP. OB-GYNs can also use a pregnancy wheel (like the one below) as a pregnancy timeline calculator to work out when you’ll have certain scans and screenings, along with your trimester dates.
How to calculate due date: Ultrasound scan
An ultrasound scan will then be used to check that the estimated due date is accurate, which is especially important if your period doesn’t always arrive at the same time each month.
“The LMP is compared to an ultrasound because some women have irregular cycles, so their LMP is not the most accurate,” Dr. Celestine explains.
“On ultrasound, I would measure the length of the fetus, called the ‘crown–rump length,’ in the first trimester to get the gestational age or due date. I then compare that date to the result I would get from just using the LMP.
“If the 2 dates are within 5 days of each other and the pregnancy is less than 9 weeks along, then we use the due date calculated by the period, not the ultrasound. But for a greater-than-5-day difference, we use the ultrasound.”
Already had your first ultrasound scan? Then you can use our Due Date by Ultrasound Calculator.
How to calculate due date: Conception date
If your cycle runs like clockwork, and you were having sex to get pregnant at a specific time, then you might have an inkling that conception happened on a certain date. But Dr. Celestine says that the conception date “isn’t used medically to calculate due date” because it’s often not accurate.
That makes sense because we know sperm can live in the female body for up to 5 days, an egg can still be fertilized for up to 24 hours after its release from the ovary, and ovulation doesn’t always happen on the same day each month (you can find out when you’re likely to be ovulating each month using our online Ovulation Calculator). That means you can still get pregnant several days after you’ve had unprotected sex.
How to calculate due date: IVF transfer date
If you’ve had in vitro fertilization (IVF), then your baby’s due date is calculated slightly differently, depending on:
- Whether you had a fresh or frozen embryo transfer
- If you had a frozen transfer, the age of the embryo when it was frozen. For example, if it was frozen on day 3, then you will be 2 weeks and 3 days pregnant on the date of transfer. For embryos frozen on day 5, it’s 2 weeks and 5 days pregnant on the date of transfer. Your clinic will be able to explain more.
The good news is that IVF due dates are generally more accurate because you’ll know exactly when you had your embryo transfer or medically conceived, although no due date is 100% accurate. Use our IVF Due Date Calculator to work out when you could be due.
How accurate is due date?
“The accuracy of the due date depends on how early in the pregnancy it was calculated and how predictable your menstrual cycle is,” Dr. Celestine explains.
“The earlier you see an OB-GYN to establish care for the pregnancy, the better because the due date [from an ultrasound scan] is more accurate early in pregnancy compared to later. It’s rare for a baby to be born exactly on their due date [only 3% to 4% of babies are].
"Usually, delivery happens within a week before or after. But there are many babies also born prematurely, [along with] medical reasons why you might need to be induced for labor early, so it really depends on the individual.”
Due date tracking with Flo
Whether you’re currently pregnant or trying to work out when you’d be due if you got pregnant today, Flo can help. Download our Trying to Conceive Mode to increase your chances of getting pregnant by tracking your most fertile days or switch to Pregnancy Mode to get week-by-week updates for both your body and your baby.
What day did I get pregnant?
As Dr. Celestine explains, it’s hard to predict the exact day you got pregnant (unless you’ve successfully conceived after fertility treatment).
“It’s all an estimate because it depends on the day you ovulated,” she says. “If you know your cycle length and it’s always the same, then usually midway through your cycle prior to pregnancy is when conception occurred.”
How many weeks do doctors allow when calculating a due date for pregnancy?
“The due date is 40 weeks from the first day of your LMP,” Dr. Celestine says. Pregnancy length therefore works out as approximately 10 months.
As we now know, that’s to account for the fact that pregnancy is counted from your LMP, not the date you conceived, so 2 extra weeks are added even though you weren’t pregnant. Also, this method recognizes that not all months have the same number of days, so you’ll likely still be pregnant at 9 months.
References
“How Long Does Pregnancy Last?” The American College of Obstetricians and Gynecologists, www.acog.org/womens-health/experts-and-stories/ask-acog/how-long-does-pregnancy-last. Accessed 13 July 2022.
“Screening Tests in Pregnancy.” NHS, www.nhs.uk/pregnancy/your-pregnancy-care/screening-tests/. Accessed 13 July 2022.
Wilcox, A. J., et al. “The Timing of the ‘Fertile Window’ in the Menstrual Cycle: Day Specific Estimates from a Prospective Study.” BMJ, vol. 321, no. 7271, 18 Nov. 2000, pp. 1259–62.
Morgan, John A., and Danielle B. Cooper. “Pregnancy Dating.” StatPearls, StatPearls Publishing, 2021.