Pregnancy Calculator
Calculate pregnancy week, trimester, and due date from LMP. Track gestational progress.
How to Use
Enter your values in the fields above and click Calculate to get instant results. All computations run locally in your browser. No data is ever uploaded or stored.
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Pregnancy Due Date Estimation
Your estimated due date is typically calculated from the first day of your last menstrual period (LMP), adding 280 days (40 weeks). CalcSolver's pregnancy calculator provides your due date along with a week-by-week timeline showing which trimester and developmental stage you're in.
Only about 5% of babies arrive exactly on their due date. Most births occur within a two-week window around the calculated date. First pregnancies tend to deliver a few days later than subsequent ones. Ultrasound measurements in the first trimester provide the most accurate dating.
Key milestones: Week 12 marks the end of the first trimester (highest miscarriage risk period has passed), Week 24 is when babies become viable outside the womb with medical support, and Week 37 is considered early term. Use CalcSolver's conception calculator to estimate when conception likely occurred.
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Frequently Asked Questions
How is the due date calculated?
The due date is estimated as 280 days (40 weeks) from the first day of your last menstrual period (LMP). This is Naegele's rule. Actual delivery dates vary — only about 5% of babies arrive on their exact due date.
How accurate is the due date?
The due date is an estimate with a margin of error of about 2 weeks. Early ultrasound measurements (8-12 weeks) provide the most accurate dating.
What are the three trimesters?
First trimester: weeks 1-12 (organ development). Second trimester: weeks 13-27 (growth and movement). Third trimester: weeks 28-40 (final growth and preparation for birth).