Pregnancy Calculator
Estimate due date (EDD), pregnancy week/day, trimester, conception estimate, and key milestones using LMP, conception date, or a known due date.
How pregnancy due date is calculated
The most common method estimates the due date by adding 280 days (40 weeks) to the first day of the last menstrual period (LMP). If cycle length differs from 28 days, this calculator can adjust the estimate by (cycle length − 28) days.
LMP vs conception date explained
LMP dating is used because many people don’t know the exact conception date. If conception is known, a conception-based estimate uses 266 days (38 weeks). Clinically, early ultrasound may be used to confirm or revise dating.
Pregnancy weeks and trimesters
Pregnancy is typically divided into three trimesters: first trimester (weeks 1–13), second trimester (weeks 14–27), and third trimester (week 28 to birth). This calculator estimates your current week and day based on the calculated LMP date and the current date you choose.
Frequently Asked Questions
Quick answers about due dates and pregnancy dating.
How is a due date calculated?
Most commonly, due date is estimated as 280 days (40 weeks) from the first day of the last menstrual period (LMP).
Why is pregnancy counted from the last menstrual period?
Because exact conception timing is often unknown, clinical dating commonly starts from LMP as a consistent reference point.
How many weeks is pregnancy?
A typical pregnancy is referenced as about 40 weeks (280 days) from LMP.
Can conception date change the due date?
Yes. If conception is known, a common estimate uses 266 days (38 weeks) from conception, which differs from LMP dating by about 14 days.
Is this pregnancy calculator accurate?
It provides an estimate only. Healthcare providers may confirm or revise dating using ultrasound and clinical information.
Disclaimer
This calculator is for informational purposes only and does not provide medical advice. For personal guidance, consult a qualified healthcare professional.