Due Date Calculator
Choose your preferred method to estimate the due date. The earliest, highest-quality ultrasound should guide the official EDD, with IVF dating overriding other methods when applicable.
How to Use This Calculator
Pick the most accurate method available
LMP is common when cycles are regular. Ultrasound dating supersedes LMP when discrepancies exceed guideline thresholds. IVF dates override other methods.
Provide supporting details
Cycle length adjusts LMP-based dating. Ultrasound and IVF data include gestational age or embryo age for precise calculation.
Discuss results with your provider
Formal dating decisions belong to your obstetric team. Use this tool to prepare questions and understand timing.
Formula
LMP method: EDD = LMP + 280 days + (cycle length − 28)
Ultrasound method: EDD = Ultrasound date − Gestational age (in days) + 280
IVF method: EDD = Transfer date + 266 − (embryo age − 3)
Equivalent LMP (IVF): LMP = Transfer date − (embryo age − 3) − 14
Full Description
Establishing an accurate estimated date of delivery guides prenatal care milestones, screening tests, and timing of delivery if complications arise. Naegele’s rule uses the LMP, but real cycles vary. Early ultrasound—especially crown-rump length—refines the date. In assisted reproduction, embryo transfer gives exact embryonic age, providing precise dating. Always let your obstetric provider confirm the official EDD.
Frequently Asked Questions
Why does my provider use a different due date?
They may rely on earlier ultrasounds, IVF clinic data, or standardized rounding. Always follow the EDD documented in your chart.
Will my due date change later?
Typically no. Once the due date is set from early ultrasound or IVF data, it remains consistent unless cleared by your clinician.
How does IVF dating differ?
Embryo transfer age is known, so conception and due date calculations reference the embryo’s developmental stage at transfer.
What if I have irregular cycles without IVF?
Ultrasound-based dating is preferred. Use the ultrasound method here and consult your provider for final dating.