Pregnancy Due Date Calculator
Our free pregnancy calculator estimates your due date and tracks your pregnancy progress. Enter the date of your last menstrual period (LMP) — the due date is calculated using Naegele's rule (LMP + 280 days, or 40 weeks). If you know your conception date, switch to the second mode: the result will be identical.
Frequently Asked Questions
How is the due date calculated?
The calculator uses Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period. In conception mode, 266 days (38 weeks) are added to the conception date, which gives the same result assuming conception occurred on day 14 of the cycle.
What is the difference between the two modes?
The "Last Period" mode is the standard medical method — doctors use the LMP date because it is easy to remember and conception is harder to pinpoint. The "Conception Date" mode is useful if you know the exact date, for example after IVF or with ovulation tracking.
How accurate is the estimated due date?
The estimated due date is a statistical average. Only about 5% of babies are born exactly on the EDD. Most births happen within 2 weeks before or after the due date. An ultrasound in the first trimester gives a more precise estimate.
What are the pregnancy trimesters?
Pregnancy is divided into three trimesters: 1st trimester (weeks 1–13) — organ formation; 2nd trimester (weeks 14–26) — active growth, the baby starts moving; 3rd trimester (weeks 27–40) — final development and preparation for birth.
When should I see a doctor?
As soon as you suspect or confirm pregnancy. Early prenatal care (ideally before week 10) helps monitor fetal development, confirm the due date with ultrasound, and detect any risks early.