Pregnancy Calculator
Estimate your due date, current pregnancy week, and key milestone dates from your last menstrual period or conception date.
Estimated Due Date
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Key milestones
Based on a standard 280-day (40-week) pregnancy. Always confirm with your healthcare provider.
What is Pregnancy Calculator?
The Pregnancy Calculator estimates your due date, current gestational week, and key milestone dates based on either your last menstrual period (LMP) or conception date. It uses the standard 280-day (40-week) pregnancy duration and shows trimester boundaries and full-term dates at a glance.
How to use
- 1 Select your calculation method: Last Period (LMP) or Conception Date.
- 2 Enter the date of the first day of your last menstrual period, or your estimated conception date.
- 3 Your estimated due date and current pregnancy week are calculated instantly.
- 4 Review the milestone timeline for end of each trimester, full term, and due date.
Formula
Example calculation
With a last menstrual period starting on March 1, the estimated due date falls on December 5 (280 days later). At 10 weeks pregnant, the first trimester ends at week 12 (around March 22 from LMP).
Frequently asked questions
How accurate is the due date estimate?
Only about 5% of babies are born on their exact due date. The estimate is based on a standard 40-week cycle; individual pregnancies vary. Your healthcare provider will refine the estimate using ultrasound measurements, which are more accurate.
What is Naegele's rule?
Naegele's rule is the standard method for calculating due date: take the first day of the last menstrual period, add one year, subtract three months, and add seven days. This is mathematically equivalent to adding 280 days.
What are the three trimesters?
The first trimester covers weeks 1-12, the second trimester covers weeks 13-26, and the third trimester runs from week 27 to delivery. This calculator marks the end of each trimester in the milestone table.
What does full term mean?
A pregnancy is considered full term from 39 weeks to 40 weeks and 6 days. Babies born between 37-38 weeks are early term. The calculator marks 37 weeks as the full term start date.
Should I use LMP or conception date?
LMP is the standard clinical method because most people know this date more precisely than conception date. If you know your conception date from fertility tracking or IVF, the conception date method may give a more accurate result.