The Due Date Calculator estimates the delivery date of a pregnant woman based on her last menstrual period (LMP), ultrasound, conception date, or IVF transfer date.
Estimate Based On:First Day of Your Last Period:Average Length of Your Cycles:Ultrasound Date:Length of Pregnancy
Estimation of due date
The due date, also known as the estimated date of confinement, is an estimation of when a pregnant woman will deliver her baby. While the due date is often estimated as a single date, it can be helpful to consider a range of due dates, since only 4% of births occur on the estimated due date.1
Due dates can be estimated using a number of different methods, including the last menstrual period, ultrasound, conception date, and IVF transfer date.
Last menstrual period
The default for this calculator bases the calculation on a woman's last menstrual period (LMP), under the assumption that childbirth on average occurs at a gestational age (age of a pregnancy calculated from the woman's last menstrual period) of 280 days, or 40 weeks. Although there is some debate regarding when pregnancy technically begins, whether at fertilization of the egg (conception), or when the egg adheres to the uterus (implantation), gestational age does not vary based on different definitions of pregnancy since it is based on LMP. In terms of gestational age, pregnancies typically last between 37 and 42 weeks, with 40 weeks often being used as an estimate in calculations. Thus, the due date is usually estimated by calculating the date that is 40 weeks from the start of a woman's LMP.
Estimating due date based on ultrasound involves the use of soundwaves to look inside the body and compare the growth of the fetus to typical growth rates of babies around the world. It is a simple process that can be performed quickly and easily, that has no known risk to babies, and can be an accurate estimate of the due date early in the pregnancy.
Using conception date to estimate due date is similar to using the last menstrual period. There is a difference of about two weeks between using these two methods that is based on the timing between the last menstrual period and the date of conception.
In vitro fertilization (IVF)
When using in vitro fertilization, the estimation of the due date is generally more precise than calculating the due date based on natural conception, since the exact transfer date is known. It still uses the average gestational age at birth of 40 weeks from a woman's last menstrual period, as do the other methods. In the case of IVF, however, the due date estimate can be made based on LMP, day of ovulation, egg retrieval, insemination, as well as the date of the 3-day or 5-day embryo transfer. In this calculator, the embryo transfer date is used.
Due date as a reference point
Generally, the point within the 37 to 42-week window at which the baby is born is not a cause for concern. Babies born between 37-39 weeks, 39-41 weeks, and 41-42 weeks are considered early term, full-term, and late-term, respectively. Under normal circumstances, babies born within any of these ranges can be healthy, though full-term babies generally have better outcomes.2 Babies born before 37 weeks are considered preterm, or premature, while those born after 42 weeks are postterm. These ranges are important as a reference for doctors to determine whether or not any action is necessary. For example, if a woman goes into labor too early at 33 weeks, doctors may stop labor to avoid a preterm baby that can have a host of health issues due to underdevelopment. Conversely, if a woman has not gone into labor after 42 weeks, doctors may induce labor. One possible complication of allowing the pregnancy to proceed beyond 42 weeks is that the placenta, which is responsible for providing nutrition and oxygen to the baby, can stop functioning properly, while the baby continues growing (requiring more nutrients and oxygen), which would eventually lead to a point in the pregnancy where the baby can no longer be adequately supported.3
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.
Calculate Based On:First Day of Your Last Period:Average Length of Your Cycles:Ultrasound Date:Length of Pregnancy
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 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.
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.
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 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.
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 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.
Can I calculate my due date from date of conception?
How is my due date calculated? 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.
How many weeks is conception to due date?
Summary. The unborn baby spends around 38 weeks in the uterus, but the average length of pregnancy, or gestation, is counted at 40 weeks. Pregnancy is counted from the first day of the woman's last period, not the date of conception which generally occurs two weeks later.
How are weeks calculated from conception?
How to Count Pregnancy Weeks. The basic formula is LMP + 280 days = EDD (estimated due date), and pregnancy week counting starts on the first day of your last period, starting with Week 0 (not 1!) and counting all the way up to Week 40 (your due date) and as high as Week 42.
How do you calculate the day you conceived a baby?
Once you know the first day of your last period, you can add 11 to 21 days to figure out your conception date. For example, a woman who is due on November 10 can calculate the first day of her last period by subtracting 40 weeks. This means her last period started on February 3.