Enter pregnancy details
Example data table
| Method | Reference date | Current date | Gestational age | Estimated due date | Current trimester |
|---|---|---|---|---|---|
| LMP | Jan 10, 2026 | Mar 9, 2026 | 8 weeks 3 days | Oct 17, 2026 | First trimester |
| Conception | Feb 1, 2026 | Mar 9, 2026 | 5 weeks 1 day | Oct 25, 2026 | First trimester |
| IVF Day 5 | Jan 28, 2026 | Mar 9, 2026 | 6 weeks 5 days | Oct 16, 2026 | First trimester |
Formula used
LMP method: Due date = LMP + 280 days + (cycle length − 28 days). This adjusts ovulation timing when cycles differ from 28 days.
Conception method: Due date = conception date + 266 days. Approximate LMP = conception date − 14 days.
IVF method: Conception date = transfer date − embryo age in days. Due date = conception date + 266 days.
Known due date method: Gestational age today is found by subtracting 280 days from the due date to estimate LMP, then counting forward.
Term categories: Preterm is before 37 weeks. Early term is 37 weeks 0 days to 38 weeks 6 days. Full term is 39 weeks 0 days to 40 weeks 6 days. Late term is 41 weeks 0 days to 41 weeks 6 days. Postterm begins at 42 weeks.
How to use this calculator
- Choose the dating method that matches your record or clinic note.
- Enter today’s date so the tool can compute current gestational age.
- Fill only the fields required for the chosen method.
- Press the calculate button to show the result above the form.
- Review gestational age, trimester, term status, and milestone dates.
- Use the CSV or PDF button to save a clean pregnancy summary.
- Compare the result with ultrasound or clinical documentation when available.
Important note
This tool is for education and planning. Ultrasound findings and clinician judgment can revise estimated dates, especially when cycle timing is uncertain or records conflict.
Frequently asked questions
1. What does this calculator estimate?
It estimates gestational age, due date, trimester, current term category, and several milestone dates using LMP, conception, IVF transfer, or an existing due date.
2. Why can the due date change later?
Due dates can change when an early ultrasound provides a more accurate pregnancy age than menstrual history, especially if cycles are irregular or dates are uncertain.
3. Is LMP always accurate?
No. LMP works best when bleeding dates are remembered correctly and cycles are reasonably regular. Ovulation timing can shift, changing the estimated pregnancy age.
4. How is IVF dating handled?
The tool subtracts embryo age from the transfer date to approximate conception, then adds 266 days to estimate the due date.
5. What is considered full term?
Full term runs from 39 weeks 0 days through 40 weeks 6 days. Early term, late term, and postterm ranges are shown separately.
6. Why include cycle length?
Cycle length helps adjust ovulation timing. A longer cycle usually pushes conception later, while a shorter cycle usually brings conception earlier.
7. Does this replace prenatal care?
No. It helps with planning and record review, but prenatal decisions should follow your clinician’s assessment, test results, and ultrasound findings.
8. Can I export the results?
Yes. After calculation, use the CSV button for spreadsheet-friendly data or the PDF button for a neat printable summary.