For educational and tracking purposes only. Results are estimates and are not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional.
Calculator tool
How this calculator works
Use the explanation to understand the formula, assumptions, and practical limits behind the calculator result.
Ways to Estimate Due Date
The calculator supports four dating routes: LMP, conception date, ultrasound dating, and IVF transfer. Each route works from a different known point and converts it into an estimated due date.
LMP and Cycle-Length Logic
With LMP dating, a 28-day cycle is the baseline. If your average cycle is longer or shorter, the calculator adjusts the estimate because ovulation may happen later or earlier than the 28-day assumption.
Why Ultrasound or IVF Can Matter
When LMP is uncertain, clinician-interpreted ultrasound dating can be more informative. IVF transfer timing is also unusually precise because the embryo age and transfer date are known.
Use the Date as a Planning Anchor
The result helps with scheduling and understanding gestational age. It does not guarantee the delivery date, and clinical dating decisions should come from the care team.
Frequently asked questions
Why do due-date estimates start from the last menstrual period?
LMP is often the earliest date people know reliably, so it is commonly used as a practical starting point. It is not the same as conception date.
How does cycle length affect the estimate?
Longer average cycles usually shift estimated ovulation later, and shorter cycles shift it earlier. That is why the calculator adjusts the LMP-based result when you enter a cycle length other than 28 days.
Is ultrasound always more accurate than LMP?
Not in every situation, but early clinician-interpreted ultrasound is especially useful when LMP is uncertain or cycles are irregular. Follow the dating method selected by the treating clinician.
Should I treat the due date as exact?
No. It is an estimate used for planning pregnancy timing. Actual delivery can happen before or after that date.
