Due Date Calculator

The estimated due date (EDD) is calculated using Naegele's rule: 280 days (40 weeks) from the first day of your last menstrual period. This assumes a regular 28-day cycle with ovulation around day 14, which is true for many but not all pregnancies.

Pregnancy is divided into three trimesters. The first trimester (weeks 1–12) is when most major organs form and the risk of miscarriage is highest. The second trimester (weeks 13–26) is often the most comfortable, with the baby growing rapidly and movements becoming noticeable. The third trimester (weeks 27–40) involves significant growth, increasing physical demands and final preparations for delivery.

Only about 4% of babies are born on their exact due date. A normal full-term pregnancy lasts anywhere from 37 to 42 weeks. Babies born before 37 weeks are considered preterm; those born after 42 weeks are post-term. Your healthcare provider can adjust your due date based on early ultrasound measurements, which are more accurate than LMP for women with irregular cycles.

This calculator is a planning tool only. It does not replace medical care or ultrasound dating. If you are pregnant, schedule an appointment with a qualified prenatal care provider as early as possible for personalized guidance and monitoring.

The estimated due date (EDD) is calculated using Naegele's rule: add 280 days (40 weeks) to the first day of the last menstrual period (LMP). This assumes a regular 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, the EDD may be a few days off. Modern obstetric care typically refines the EDD using an early ultrasound, which measures fetal size and is most accurate when performed between 8 and 13 weeks.

Pregnancy is divided into three trimesters. The first trimester (weeks 1–13) is when most organ development happens — and unfortunately also when miscarriage risk is highest and morning sickness is most common. The second trimester (weeks 14–27) is often the most comfortable, with energy returning and the first fetal movements ("quickening") appearing around week 18–22. The third trimester (weeks 28–40) is marked by rapid fetal growth, prenatal visits becoming more frequent, and preparation for delivery.

Only about 4% of babies are born on their exact due date. Most full-term births occur between 37 and 42 weeks, with 39–40 weeks being most common. Babies born before 37 weeks are considered premature; those born after 42 weeks are post-term and usually induced for safety. The wide window is normal — your body, hormones, and baby together determine the actual birth date.

Use this calculator as a planning aid for maternity leave, baby preparation, and prenatal appointments. Confirm your due date with your healthcare provider, who will use ultrasound measurements and clinical judgment for the most accurate estimate. Regular prenatal care — typically monthly visits in the first and second trimesters, bi-weekly in weeks 28–36, and weekly after week 36 — is the single best predictor of healthy outcomes for mother and baby.