Pregnancy due date calculator

Congratulations on your pregnancy! Now that you’re rocking that pregnancy glow, you can start planning for the arrival of your little miracle. You’re probably wondering how to know your due date.

Use our pregnancy due date calculator to find out when your baby’s arrival will come.

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This is not a diagnosis. The calculations that are provided are estimates based on averages.

How is my due date calculated?

Our baby due date calculator gives you the option of two methods to determine when your newborn will arrive: the date of your last menstrual period or your conception date, also known as ovulation date. This method allows you to find out how far along you are, but also when to expect baby to make their grand entrance.

Take a look below at how each of these methods works.

This post has been reviewed for accuracy by the following medical professional:

Dr. Heather Soper  

Dr. Heather Soper

Certified Nurse Midwife

Heather has 15 years of women’s health and obstetrics experience. She is the owner of The Genesis Resort for Birth and an Assistant Professor of Nursing at James Madison University.

Last menstrual period

Using the first day of your last menstrual period is the most common method for calculating your baby’s due date. Why?

On average, pregnancies last around 40 weeks, or 280 days. To learn your baby’s due date, you can:

  • Grab your calendar
  • Find the date that marks the first day of your last period
  • Count forward 40 weeks or 280 days

You can also count back 3 calendar months from the first day of your last period, then add 1 year and seven days to that date.

 

Date of conception

If you were tracking your cycle you may know your ovulation date and use this date of conception to estimate your due date. This is the part of your menstrual cycle when a mature egg leaves your ovary in the hopes of becoming fertilized in the 12 to 24 hours after release. If fertilization doesn’t occur within this time period, the egg dissolves.

The date of conception is essentially the date you ovulated, which can be used to calculate your estimated due date. Ovulation typically occurs on day 14 of a 28-day menstrual cycle, so adding 266 days to your conception date will give you your baby’s due date. (You add 266 days because the average pregnancy is 280 days, minus the 14 days of your cycle).

 

Accuracy of due date estimations

Few pregnancies are delivered on their given due date. To track a baby’s development, we can only rely on dates and milestones based on averages and estimates.

For a better understanding of due date accuracy, take a look at a few of the reasons why due date estimations are, well, estimations.

  • Calculation by ‘last menstrual period’ is based on a regular 28-day menstrual cycle, with ovulation occurring 14 days into the cycle. Because this doesn’t account for cycle length irregularities and variability in ovulation timing, discrepancies can exist.
  • The development of human life isn’t programmed. And neither is a baby’s birth. A growing baby is both art and science. While there may be trends researchers can point to (such as developing hearing around week 18), the exact time at which babies develop is variable.

Once you schedule your first appointment with your midwife or doctor, they will also provide you with an estimated due date so you can plan accordingly.

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Top gender FAQs

Find answers to any questions you may have

  • I Used the Pregnancy Calculator… Now What?
    Congratulations on your pregnancy! Firstly, schedule an appointment with your healthcare provider, be it a doctor or midwife, to start monitoring your pregnancy's progress and ensure both you and the baby remain healthy. Your doctor will also confirm how far along you are, and when your estimated due date will be. If you're keen, you can also consider early gender determination methods, like the SneakPeek At Home Gender Test, to connect more deeply with your unborn child. Our test is over 99% accurate at determining gender at just 6 weeks! Remember also to explore prenatal care options and start planning key events like baby showers or gender reveal parties.
  • Can I use a pregnancy calculator if I have irregular periods?
    Yes, you can. However, it's crucial to remember that the results might be less accurate due to the variable lengths of menstrual cycles. If you have irregular periods, it's advisable to seek medical guidance for a more accurate due date prediction.
  • How is the due date calculated if I conceived through IVF or fertility treatments?
    You can use this same method to find out how far along you are with IVF or fertility treatment. For pregnancies conceived through IVF or other fertility treatments, the due date is typically calculated by counting 40 weeks from the date of egg retrieval or fertilization.
  • What are other ways doctors can determine my due date?
    Doctors estimate due dates using various methods. One common approach is an ultrasound scan between weeks 6 and 8 of pregnancy, measuring the baby's growth to estimate gestational age. For those undergoing IVF treatments, the embryo transfer date is crucial. Specifically, a 3-day embryo transfer adds 263 days, while a 5-day transfer adds 261 days to calculate the due date.

Discover your baby’s gender

SneakPeek is the only at-home gender test with data validated and published in scientific journals, for results you can trust.

Resources

Johns Hopkins Medicine
Calculating a Due Date. https://www.hopkinsmedicine.org/health/wellness-and-prevention/calculating-a-due-date

Healthline
How Long Does Ovulation Last Each Month? https://www.healthline.com/health/pregnancy/how-long-does-ovulation-last#how-long-ovulation-lasts

Healthline
What Is Ovulation? 16 Things to Know About Your Menstrual Cycle. https://www.healthline.com/health/womens-health/what-is-ovulation#duration

Pew Research Center
A third of U.S adults say they have used fertility treatments or know someone who has. https://www.pewresearch.org/fact-tank/2018/07/17/a-third-of-u-s-adults-say-they-have-used-fertility-treatments-or-know-someone-who-has/

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Very Well Family
Early Pregnancy Ultrasound Results. https://www.verywellfamily.com/understand-early-pregnancy-ultrasound-results-2371367

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CDC. Births
Final Data for 2017. https://www.cdc.gov/nchs/data/nvsr/nvsr67/nvsr67_08-508.pdf

ACOG
When Pregnancy Goes Past Your Due Date. https://www.acog.org/womens-health/faqs/when-pregnancy-goes-past-your-due-date?utm_source=redirect&utm_medium=web&utm_campaign=otn

ACOG
Methods for Estimating the Due Date. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/05/methods-for-estimating-the-due-date

Healthline
When Baby Comes Early: What Is Your Risk? https://www.healthline.com/health/pregnancy/preterm-labor-risk-factors#TOC_TITLE_HDR_1

NCBI
Maternal body mass index and post-term birth: a systematic review and meta-analysis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5324665/

ScienceDirect
Prolonged Pregnancy. https://www.sciencedirect.com/topics/medicine-and-dentistry/prolonged-pregnancy