Estimate conception timing using scan age and dates. See due date, LMP, and useful ranges. Helpful for records, questions, and thoughtful pregnancy preparation today.
This calculator estimates conception timing from an ultrasound date and gestational age. It also shows an estimated last menstrual period, a likely conception window, and an estimated due date. It is designed for planning, record review, and discussion support.
These results are approximate. Pregnancy dating can vary with scan timing, cycle variation, and clinical context. Use your care team’s official dating record when dates differ.
| Ultrasound Date | Gestational Age | Cycle Length | Estimated Conception | Estimated Due Date |
|---|---|---|---|---|
| 2026-04-10 | 8 weeks 4 days | 28 days | 2026-02-15 | 2026-11-20 |
| 2026-03-18 | 11 weeks 2 days | 30 days | 2025-12-31 | 2026-10-05 |
| 2026-02-28 | 6 weeks 6 days | 26 days | 2026-01-19 | 2026-10-18 |
1. Convert ultrasound gestational age into total days.
Total gestational days = (weeks × 7) + days
2. Estimate the last menstrual period from the scan date.
Estimated LMP = Ultrasound date − total gestational days
3. Estimate conception from the LMP using cycle length.
Estimated conception = Estimated LMP + (cycle length − 14)
4. Estimate due date from the LMP.
Estimated due date = Estimated LMP + 280 days
This method uses ultrasound age as the main anchor and then adjusts the likely conception day with the cycle length input. It is a practical estimate, not a clinical confirmation.
It estimates conception timing from an ultrasound date plus gestational age. It also shows an estimated last menstrual period, due date, and a small likely conception window. These dates are approximations and should support, not replace, clinical interpretation.
Early ultrasound dating is often more consistent than memory-based cycle dates, especially when periods are irregular. Later scans can be less precise for dating. Clinical teams usually decide which dating method to use for the pregnancy record.
Fertilization does not always happen on one predictable calendar moment. Ovulation timing, sperm survival, and cycle variation can shift the likely day. That is why the page shows an estimate and a nearby likely window.
Yes. A shorter or longer cycle can shift the likely ovulation day away from the usual midpoint assumption. The cycle length field adjusts the estimated conception date while ultrasound-based pregnancy age remains the main reference point.
No. IVF, frozen embryo transfer, and related treatments use different dating rules. Those situations should be dated with transfer details and medical guidance instead of a natural-conception estimate from this calculator.
You can enter a later scan, but precision may drop as pregnancy progresses. Earlier scans are commonly better for dating. If several scans disagree, use the official dating method given by your care team.
The due date comes from the same pregnancy timeline. It helps you cross-check whether the scan date, gestational age, and conception estimate fit together on one calendar and supports clearer record review.
No. This page is an educational planning tool. Only a qualified clinician can confirm pregnancy dating, explain scan findings, and interpret differences between ultrasound dates, symptoms, and personal records.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.