Pregnancy Due Date Calculator — Free Online Due Date Estimator
Calculate your due date, current week, trimester, and see fetal development milestones. Track your pregnancy journey week by week. All calculations happen locally — nothing leaves your browser.
How to Use the Due Date Calculator
- Enter your LMP date — the first day of your last menstrual period.
- See your due date — calculated as 280 days (40 weeks) from LMP.
- Track your progress — current week, trimester, and weeks remaining.
- View milestones — see fetal size comparison and development updates.
Understanding Your Due Date
A due date is an estimate, not a deadline. Only about 5% of babies arrive on their exact due date. Most arrive within 1-2 weeks before or after. The standard calculation uses Naegele's rule: LMP + 7 days, then subtract 3 months (or simply LMP + 280 days).
Pregnancy is counted from the first day of the LMP, which is about 2 weeks before actual conception. This is why you're "2 weeks pregnant" at conception — the standard counting method starts from the last period.
Frequently Asked Questions
If you're unsure of your LMP, an early ultrasound can date the pregnancy more accurately. You can also estimate based on when you first noticed symptoms (usually 2-4 weeks after conception).
Early ultrasounds (first trimester) are most accurate for dating. Later ultrasounds may adjust the date by a few days. Your provider may update the due date if the ultrasound dating differs significantly from LMP dating.
Due date calculators provide an estimate based on Naegele's rule (280 days from the last menstrual period), which is accurate to within about 1-2 weeks for most pregnancies. Only about 5% of babies arrive on their exact due date. The estimate is most accurate when based on an early ultrasound rather than the last menstrual period.
Use Cases
Due Date Prediction
Predict your pregnancy due date based on your last menstrual period to plan for the arrival of your baby.
Gestational Milestones
Track gestational milestones week by week to understand fetal development and pregnancy progress.
Prenatal Appointment Planning
Plan prenatal appointments and checkups based on your current gestational week and upcoming milestones.
Conception Date Calculation
Calculate conception date from due date to understand your pregnancy timeline and important dates.
Expecting Parents Timeline
Create a comprehensive timeline for expecting parents to prepare for pregnancy, birth, and postpartum periods.