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Due Date Calculator

Estimate your due date (EDD) and current pregnancy week. Free and no sign-up required.

Estimated due date
SA 0SA 13SA 27SA 40

How is the due date calculated?

The estimated due date (EDD) is calculated using Naegele's rule: add 280 days (or 40 weeks of amenorrhea) to the first day of your last period. If you know the exact date of conception, add 266 days (38 weeks). This method assumes a regular 28-day cycle with ovulation on day 14.

Pregnancy trimesters explained

Pregnancy is divided into three trimesters. The first trimester (weeks 1-13) is the period of organ formation: it's a crucial stage where nausea and fatigue are common. The second trimester (weeks 14-27) is often considered the most comfortable: nausea decreases and you start feeling the baby's movements. The third trimester (weeks 28-40) is dedicated to organ maturation and preparation for birth.

Weeks of amenorrhea vs pregnancy weeks

In France, healthcare professionals count in weeks of amenorrhea (WA), i.e. from the first day of the last period. Pregnancy weeks (PW) count from conception, about 2 weeks less. For example, WA 12 corresponds to PW 10. Our calculator displays both for clarity.

What accuracy to expect?

It's important to know that only 5% of babies are born on the exact due date. The majority are born between 37 and 42 weeks of pregnancy, which is considered normal. The first trimester ultrasound (between weeks 11 and 14) can verify and adjust the EDD with an accuracy of plus or minus 5 days.

Frequently Asked Questions

How do I calculate my due date?
The most common method is Naegele's rule: add 280 days (40 weeks) to the date of the first day of your last period. If you know the date of conception, add 266 days (38 weeks). The first trimester ultrasound can then confirm or adjust this estimate.
What week of pregnancy am I?
Pregnancy week is calculated from the first day of your last period (WA = weeks of amenorrhea). For example, if your last period was 10 weeks ago, you are at WA 10, which corresponds to about 8 pregnancy weeks (PW). Our calculator shows both values.
How accurate is this calculator?
This calculator gives an estimate based on averages. Only 5% of babies are born exactly on their EDD. Most are born between 37 and 42 weeks. The first trimester ultrasound (between weeks 11 and 14) offers the best accuracy for dating pregnancy.
What are the 3 trimesters of pregnancy?
The first trimester goes from week 1 to 13 (organ formation). The second trimester goes from week 14 to 27 (growth and first noticeable movements). The third trimester goes from week 28 to 40 (organ maturation and preparation for birth).

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This tool provides indicative estimates and does not replace medical advice. Consult a healthcare professional for any questions.

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