Due Date Calculator
This free due date calculator estimates the due date based on the menstrual cycle, ultrasound, conception date, or IVF transfer date.
Based on standard Naegele's rule (LMP + 280 days). Assumes a 28-day cycle.
How to Use the Due Date Calculator
Enter the first day of your last menstrual period (LMP), known conception date, or IVF-related timing data if available. The calculator estimates due date, current gestational age, trimester stage, and key pregnancy milestones.
Dating Methods Overview
LMP-based and conception-based methods are common starting points for estimating expected delivery timelines.
Clinical Refinement Process
Prenatal care may refine estimated dates using ultrasound and medical history, especially when cycle history is uncertain.
Milestone Planning
Due-date calculators help schedule checkups, tests, and preparation milestones, but medical advice remains primary.
Understanding Date Variability
Normal delivery timing spans a range, so estimate windows are more practical than exact-day expectations.
Safe Interpretation
Use date estimates for planning context and coordinate with your obstetric provider for personalized care decisions.
Frequently Asked Questions
How is the due date calculated?+
Most estimates use the first day of LMP and add 280 days, assuming a typical cycle and ovulation timing.
Why is my baby not born exactly on due date?+
Due date is an estimate, not an exact prediction. Many normal births occur before or after the estimated day.
Can irregular cycles affect due date estimates?+
Yes. Irregular cycles can shift ovulation timing, making LMP-only estimates less precise.
Does ultrasound provide better dating?+
Early ultrasound can improve gestational dating accuracy and may adjust estimated due date.
How accurate are online due date calculators?+
They are useful for planning but should be interpreted with clinical confirmation during prenatal care.
Can IVF pregnancies use the same method?+
IVF dating often uses known transfer or fertilization timing, which may produce more specific estimates.
What is gestational age vs fetal age?+
Gestational age counts from LMP, while fetal age is typically about two weeks less and counts from conception.
What trimester am I in?+
Trimester ranges are commonly: first (0-13 weeks), second (14-27 weeks), third (28+ weeks).
Should I recalculate due date frequently?+
Recalculation is usually unnecessary unless clinical dating is updated by your care team.
When should I contact my provider?+
Contact your provider for concerning symptoms, uncertainty about dates, or questions about milestone timing.
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