Pregnancy Due Date Calculator
Pregnancy Due Date Calculator
Estimate your due date and pregnancy timeline from your last menstrual period or a known conception date.
Pregnancy is commonly dated as 40 weeks from the first day of the LMP. First-trimester ultrasound may confirm or revise your due date. For IVF or irregular cycles, follow your maternity team’s date. See ACOG dating guidance and the NHS due date guide.
Pregnancy Due Date Calculator FAQs
1. How is a pregnancy due date calculated?
A pregnancy due date is usually estimated by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP). Cycle length may affect this estimate.
2. How accurate is a Pregnancy Due Date Calculator?
A due date is an estimate, not an exact delivery date. According to ACOG, only about 1 in 20 babies are born on their estimated due date.
3. How many weeks does pregnancy normally last?
Pregnancy is typically dated as 40 weeks from the last menstrual period. Birth may occur before or after the estimated due date, with pregnancies commonly lasting 37–42 weeks.
4. Can I calculate my due date from conception?
Yes. If the conception date is reliably known, adding approximately 266 days (38 weeks) provides an estimated due date. The actual timing of conception may be uncertain.
5. What are the three pregnancy trimesters?
The first trimester lasts through 13 weeks and 6 days. The second trimester covers weeks 14–27, and the third trimester begins at 28 weeks.
6. Does menstrual cycle length affect the due date?
Yes. Standard due date calculations assume a 28-day menstrual cycle. Shorter or longer cycles may change the estimate, while irregular cycles can make LMP-based dating less reliable.
7. Is ultrasound more accurate than a due date calculator?
Yes. A first-trimester ultrasound is generally the most accurate method for confirming gestational age. For IVF pregnancies, clinicians use embryo age and transfer dates for pregnancy dating.
8. When should I see a doctor during pregnancy?
Arrange prenatal care after confirming pregnancy. Your healthcare provider can review your medical history, assess pregnancy dating, and recommend appropriate checkups and ultrasound scans.