Pregnancy Calculator (2024)

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The Pregnancy Calculator can estimate a pregnancy schedule based on the provided due date, last period date, ultrasound date, conception date, or IVF transfer date.

Pregnancy Calculator (1)

RelatedOvulation Calculator | Conception Calculator

Pregnancy Term & Due Date

Pregnancy is a term used to describe a woman's state over a time period (~9 months) during which one or more offspring develops inside of a woman. Childbirth usually occurs approximately 38 weeks after conception, or about 40 weeks after the last menstrual period. The World Health Organization defines a normal pregnancy term to last between 37 and 42 weeks. During a person's first OB-GYN visit, the doctor will usually provide an estimated date (based on a sonogram) at which the child will be born, or due date. Alternatively, the due date can also be estimated based on a person's last menstrual period.

While the due date can be estimated, the actual length of pregnancy depends on various factors, including age, length of previous pregnancies, and weight of the mother at birth.1 However, there are still more factors affecting natural variation in pregnancy terms that are not well understood. Studies have shown that fewer than 4% of births occur on the exact due date, 60% occur within a week of the due date, and almost 90% occur within two weeks of the due date.2 As such, while it is possible to be fairly confident that a person's child will be born within about two weeks of the due date, it is currently not possible to predict the exact day of birth with certainty.

Pregnancy Detection

Pregnancy can be detected either by using pregnancy tests or by the woman herself noticing a number of symptoms, including a missed menstrual period, increased basal body temperature, fatigue, nausea, and increased frequency of urination.

Pregnancy tests involve the detection of hormones that serve as biomarkers for pregnancy and include clinical blood or urine tests that can detect pregnancy from six to eight days after fertilization. While clinical blood tests are more accurate, and can detect exact amounts of the hormone hCG (which is only present during pregnancy) earlier and in smaller quantities, they take more time to evaluate and are more expensive than home pregnancy urine tests. It is also possible to get a clinical urine test, but these are not necessarily more accurate than a home pregnancy test, and can potentially be more costly.

Pregnancy Management

There are a number of factors that need to be considered during pregnancy, many of which are highly dependent on the individual's situation, such as medication, weight gain, exercise, and nutrition.

Medication:

Taking certain medications during pregnancy can have lasting effects on the fetus. In the U.S., drugs are classified into categories A, B, C, D, and X by the Food and Drug Administration (FDA) based on potential benefits vs. fetal risks. Drugs that have positive benefits for the mother with low risk to the fetus are classified as category A, while drugs with proven, significant fetal risks that outweigh potential benefits to the mother are classified as category X. A person that is pregnant should consult their doctor regarding any medications they plan to use during their pregnancy.

Weight gain:

Weight gain is a largely inevitable and necessary aspect of pregnancy that varies between people. It affects many aspects of fetal development, such as the weight of the baby, the placenta, extra circulatory fluid, and its fat and protein stores. Weight management merits consideration because insufficient or excessive weight gain can have negative effects for both mother and fetus, including the need for cesarean section (C-section) and gestational hypertension. While the values vary between women, the Institute of Medicine recommends an overall pregnancy weight gain of 25-35 pounds for women who are considered "normal" weight (BMI 18.5-24.9), 28-40 pounds for those considered underweight (BMI < 18.5), 15-25 pounds for those considered overweight (BMI 25-29.9), and 11-20 pounds for those considered obese (BMI > 30).3 Our Pregnancy Weight Gain Calculator is based on the Institute of Medicine recommendations.

Exercise:

Studies indicate that aerobic exercise during pregnancy helps to improve or maintain physical fitness as well as possibly decreasing the risk of C-sections. Although it varies between women, regular aerobic and strength-conditioning exercise are often recommended for pregnant women, and women who exercised regularly before pregnancy, who have uncomplicated pregnancies, should be able to continue high-intensity exercise programs.4 The American College of Obstetricians and Gynecologists suggests that given an uncomplicated pregnancy, fetal injuries are unlikely to occur as a result of exercise. Nevertheless, caution is advised, and a pregnant woman should consult their doctor if any of the following symptoms present: vaginal bleeding, shortness of breath, dizziness, headache, calf pain or swelling, amniotic fluid leakage, decreased fetal movement, preterm labor, muscle weakness, or chest pain.5

Nutrition:

Nutrition during pregnancy is particularly important for the health of the mother and baby. Pregnancy requires different nutritional considerations than a person would have in a non-pregnant state due to increased energy and specific micronutrient requirements.6

Certain vitamins such as Vitamin B9, also known as folic acid, can help decrease the risk of certain defects, while other nutrients such as DHA omega-3 that is necessary for proper brain and retinal development cannot be produced efficiently by infants, and can only be obtained through the placenta during pregnancy, or in breast milk after birth. There are many other micronutrients that aid proper fetal development, and there exist myriad sources of information on what pregnant women should or shouldn't eat or do. All of the information can be different to sift through and can vary from person to person. Pregnant women should consult their doctors and/or dietitian to help determine the best course of action for their own specific needs.


  1. Jukic, AM, Baird, DD, Weinberg, CR, et al. 2013. "Length of human pregnancy and contributors to its natural variation. Human Reproduction 28(10): 2848-55. PMC3777570.
  2. Moore, Keith. 2015. "How accurate are 'due dates'?" BBC, February 3, 2015. www.bbc.com/news/magazine-31046144.
  3. Institute of Medicine. 2009. "Weight Gain During Pregnancy: Reexamining the Guidelines." National Academies Press.
  4. Davies, GA, Wolfe, LA, Mottola, MF, et al. 2003. "Exercise in pregnancy and the postpartum period." Journal of Obstetrics and Gynaecology Canada 25(6): 516-29.
  5. Artal, R., O'Toole, M. 2003. "Guidelines of the American College of Obstetricians and Gynecologists for exercise during pregnancy and the postpartum period." British Journal of Sports Medicine 37: 6-12. doi:10.1136/bjsm.37.1.6
  6. Lammi-Keefe, CJ, Couch, SC, Philipson, E. 2008. "Handbook of Nutrition and Pregnancy." Humana Press.
Pregnancy Calculator (2024)

FAQs

Is a pregnancy calculator accurate? ›

A due date calculator may not be completely accurate. This is especially true if you aren't exactly sure when you had your last period, you have irregular periods or you don't know when you conceived. You should see your pregnancy care provider for a more precise test, such as an ultrasound, to confirm your due date.

How do I calculate the exact day I got pregnant? ›

Generally, the due date is calculated 40 weeks after your last period. Therefore, if you have your due date, you can subtract 40 weeks from this date to determine your last menstrual period. Once you know the first day of your last period, you can add 11 to 21 days to figure out your conception date.

What is the correct way to calculate pregnancy? ›

A typical pregnancy lasts, on average, 280 days, or 40 weeks—starting with the first day of the last normal menstrual period as day 1. An estimated due date can be calculated by following steps 1 through 3: First, determine the first day of your last menstrual period. Next, count back 3 calendar months from that date.

How to confirm pregnancy calculator? ›

Pregnancy calculator is an online calculator to confirm pregnancy before you use a home pregnancy kit. This calculator is based on your last menstrual period, existing symptoms and the tests if any you may have undertaken.

Can ultrasound be wrong on due date? ›

Between 22 0/7 weeks and 27 6/7 weeks of gestation, ultrasonography dating has an accuracy of ± 10–14 days 19.

When am I due based on conception? ›

Conception Date: If you have been using an ovulation predictor kit or tracking your ovulation you may be able calculate your due date based on the precise date of conception. In order to do this simply count 266 days, or 38 weeks, from the conception date to find your estimated due date.

What day was my baby conceived? ›

Conception usually occurs around 11-21 days after the first day of the last period of a woman who has a regular period. The estimation of conception date is based on this, but is rarely ever exact since it is difficult to know exactly when ovulation occurs.

What is the first day of pregnancy usually calculate as? ›

Pregnancy (or gestation) is calculated as 40 weeks and starts from the first day of your last menstrual period.

When do pregnancy symptoms start? ›

You may feel sick or be sick. Although commonly known as "morning sickness", vomiting and morning sickness can happen at any time of the day or night. Symptoms usually start when you're around 4 to 6 weeks pregnant.

How to tell if you're pregnant early on? ›

Symptoms of early pregnancy include missed periods, nausea and vomiting, breast changes, tiredness and frequent urination. Many of these symptoms can also be caused by other factors such as stress or illness.

How to count the first week of pregnancy? ›

Your weeks of pregnancy are dated from the first day of your last period. This means that in the first 2 weeks or so, you are not actually pregnant – your body is preparing for ovulation (releasing an egg from one of your ovaries) as usual. Your "getting pregnant" timeline is: day 1: the first day of your period.

Which week pregnant am I? ›

To calculate your pregnancy weeks, just count from the first day of your last period to the current date in weeks. That way you will get how many weeks of pregnancy is over. How does the pregnancy due date calculator work? Add 280 days (40 weeks) to the first day of your last menstrual period (assuming a 28-day cycle).

How do you 100% know if you're pregnant? ›

Store-bought pregnancy tests are just as accurate as a urine pregnancy test that you'd get at a doctor's office. Pregnancy tests are most accurate when you take them after you've already missed your period. A pregnancy test will be less accurate if it's expired or if you don't use it the right way.

How can I know the exact day I got pregnant? ›

In a Typical Pregnancy

Most women do not know the exact date of conception because it can be challenging to know exactly when ovulation occurs. Thus, their conception date is merely an estimate based on the first day of their last period.

How do I know I'm 100% pregnant? ›

There's no way to know for certain if you're pregnant before missing your period other than taking a home pregnancy test. Some women do experience symptoms such as fatigue and nausea. These could be PMS symptoms, however. If you still aren't sure you're pregnant after taking a home test, see a doctor.

How accurate are pregnancy measurements? ›

Nothing is 100% accurate when it comes to estimating your baby's size in utero. It's common for your baby's size to be off by a centimeter or two. Your healthcare provider will do further testing if there is a reason to be concerned.

How accurate are pregnancy estimates? ›

pregnancies, the American College of Obstetricians and Gynecologists says that fetal measurements taken during a first trimester ultrasound are the most accurate way to estimate a due date, especially for people with irregular menstrual cycles. Sometimes, initial due dates are revised after this ultrasound.

What is the most accurate way to determine pregnancy? ›

The pregnancy tests you get at the drugstore work 99 out of 100 times. They're just as accurate as a urine pregnancy test that you'd get at a doctor's office. Pregnancy tests work by checking your urine (pee) for a hormone called human chorionic gonadotropin (HCG). Your body only makes this hormone if you're pregnant.

How do I know if I am 100% pregnant? ›

The only way to know for sure if you're pregnant is by taking a pregnancy test. You can go to your local Planned Parenthood, doctor's office, or other community health center to get a pregnancy test, or you can buy a pregnancy test at your local drugstore.

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