This tool provides planning estimates only. It does not replace medical advice, prenatal care, scan interpretation, or urgent assessment from a qualified clinician.
Calculator form
Example data table
| Scenario | Method | Main entry | Extra detail | Illustrative outcome |
|---|---|---|---|---|
| Standard cycle tracking | LMP | January 8, 2026 | 28-day cycle | Due date around October 15, 2026 |
| Clinic issued estimate | Due date | October 30, 2026 | No extra input needed | Calculator rebuilds LMP and milestones |
| Known ovulation timing | Conception | February 2, 2026 | Conception date confirmed | Due date around October 26, 2026 |
| Embryo transfer planning | IVF | March 4, 2026 | 5-day embryo | Due date uses transfer plus embryo age |
| Early scan dating | Ultrasound | March 10, 2026 | 8 weeks 3 days | Calculator backdates LMP and due date |
Formula used
This calculator uses standard pregnancy dating conventions. It estimates gestational age, due date, trimester position, progress percentage, and key prenatal milestones from your chosen input method.
| Method | Formula |
|---|---|
| LMP | Estimated due date = LMP + 280 days + (cycle length − 28 days). |
| Due date | Estimated LMP = due date − 280 days. |
| Conception date | Estimated due date = conception date + 266 days. Estimated LMP = conception date − 14 days. |
| IVF transfer | Estimated due date = transfer date + (266 − embryo age). Estimated LMP = transfer date − (14 + embryo age). |
| Ultrasound dating | Estimated LMP = scan date − gestational age at scan. Estimated due date = estimated LMP + 280 days. |
| Progress percentage | Progress = gestational days ÷ expected pregnancy length × 100. |
| Remaining time | Days remaining = estimated due date − today. |
How to use this calculator
- Choose the dating method that matches your records.
- Enter the relevant date and any extra values shown.
- Press the calculate button to create the progress summary.
- Review gestational age, due date, trimester, and milestone dates.
- Use the chart to visualize how far pregnancy has progressed.
- Download the summary as a CSV or PDF for planning.
- Recheck dates with your clinician if scans or records differ.
Frequently asked questions
1. Which dating method is usually best?
Use the method your clinician relies on. Early ultrasound and IVF transfer dates are often the most precise. LMP works well when cycles are regular and the first day is known clearly.
2. Why can due dates change after a scan?
Scans measure fetal size and can refine gestational age, especially early in pregnancy. A clinician may update the expected due date when scan findings fit a different timeline better than calendar dates.
3. Is pregnancy always exactly 280 days?
No. Two hundred eighty days is a standard estimate from LMP. Natural variation, cycle length, ovulation timing, and clinical dating adjustments can shift the predicted end date.
4. What does gestational age mean?
Gestational age counts from the last menstrual period, not usually from conception. That is why pregnancy weeks often start about two weeks before fertilization likely occurred.
5. Why does IVF use embryo age?
Embryo transfer dating already includes how many days the embryo developed before transfer. Adding that age helps estimate conception timing, gestational age, and the expected due date more accurately.
6. Can I use this after my due date passes?
Yes. The calculator shows overdue days once the estimated due date has passed. It remains a planning tool and should not guide decisions about monitoring or delivery timing.
7. Does this tool predict labor day exactly?
No. It estimates a due date, not an exact birth day. Many births occur before or after the estimated date, even when pregnancy dating is accurate.
8. Should I trust the chart over medical advice?
No. The chart is useful for organization, milestone tracking, and discussion. Follow your clinician’s guidance for symptoms, scan timing, screening choices, reduced movements, or urgent concerns.