Due Date Calculator
Calculate your due date, current pregnancy week, trimester, and key milestones from your LMP.
Based on Naegele's Rule (LMP + 280 days)
Enter your LMP date to begin
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This calculator is for informational purposes only. Only a healthcare provider can confirm your due date. Always consult your OB/GYN or midwife for medical guidance.
Frequently Asked Questions
How is the due date calculated from the last menstrual period?
The standard Naegele's Rule adds 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is the same as adding 9 months and 7 days.
How are pregnancy weeks counted?
Pregnancy is counted from the first day of your LMP, not conception. A full-term pregnancy is 40 weeks. Week 1 starts on the LMP date, and each week adds 7 days.
What are the three trimesters of pregnancy?
The first trimester is weeks 1–12, the second trimester is weeks 13–26, and the third trimester is weeks 27–40 (or until birth). Each trimester brings distinct developmental milestones.