Calculator Inputs
Choose one dating method. The form uses a responsive calculator grid: three columns on large screens, two on medium, and one on mobile.
Example Data Table
These sample rows show how different methods can produce usable timeline estimates for planning and review.
| Method | Input | As Of Date | Approx. Result | Estimated Due Date |
|---|---|---|---|---|
| LMP | January 5, 2026 | March 15, 2026 | Month 3, 9w 6d, First Trimester | October 12, 2026 |
| Due Date | September 28, 2026 | March 15, 2026 | Month 3, 12w 1d, First Trimester | September 28, 2026 |
| Ultrasound | Scan on March 1, 2026 at 8w 4d | March 15, 2026 | Month 3, 10w 4d, First Trimester | October 7, 2026 |
Formula Used
This calculator supports several pregnancy dating methods. All outputs are estimates and should be confirmed with your clinician.
- LMP method: Estimated Due Date = LMP + 280 days + cycle adjustment.
- Cycle adjustment: Cycle Length − 28 days. This shifts ovulation-based estimates for longer or shorter cycles.
- Gestational age: As Of Date − estimated LMP, expressed in weeks and extra days.
- Conception method: Due Date = Conception Date + 266 days.
- Ultrasound method: Derived LMP = Scan Date − gestational age measured at scan.
- Pregnancy month mapping: The result uses clinical week bands to place the pregnancy into Month 1 through Month 10.
| Pregnancy Month | Clinical Week Range |
|---|---|
| Month 1 | Weeks 0–4 |
| Month 2 | Weeks 5–8 |
| Month 3 | Weeks 9–13 |
| Month 4 | Weeks 14–17 |
| Month 5 | Weeks 18–22 |
| Month 6 | Weeks 23–27 |
| Month 7 | Weeks 28–31 |
| Month 8 | Weeks 32–35 |
| Month 9 | Weeks 36–40 |
| Month 10 | Weeks 41–42 |
How to Use This Calculator
- Select the calculation method that matches the information you already have.
- Enter the relevant date fields, plus the cycle length when using LMP or due-date estimation.
- Choose the “as of” date to evaluate the pregnancy timeline for today or any future review date.
- Click Calculate Pregnancy Month to display the result directly below the header and above the form.
- Review the month, gestational age, trimester, due date, conception estimate, and progress graph.
- Use the CSV or PDF buttons to export the result summary for records or appointment discussions.
FAQs
1) What does a pregnancy month calculator show?
It estimates pregnancy month, gestational age, trimester, due date, conception date, and progress. It turns common dating inputs into an easier month-based timeline for planning.
2) Why are pregnancy months not exact calendar months?
Pregnancy is usually tracked in weeks and days. Month groupings are approximations, so different charts may label the same week slightly differently.
3) Which method is best to use?
Use the most reliable information you have. LMP is common, conception date helps when known, and ultrasound dating is often helpful when early scan data is available.
4) Does cycle length matter?
Yes. A longer or shorter cycle can shift ovulation timing. This calculator adjusts LMP and due-date estimates when you enter a cycle length other than 28 days.
5) Is ultrasound dating more accurate?
It can be, especially when the scan is early. Accuracy depends on scan timing, measurement quality, and clinical interpretation by your care team.
6) Why is there a Month 10 result?
Some clinical month maps place weeks 41–42 into a tenth month. This helps describe post-term timing, even though pregnancy is still mainly tracked by weeks.
7) Can this replace medical advice?
No. It is a planning and education tool. Your clinician should confirm due date, gestational age, and any care decisions.
8) What if I pass the due date?
The calculator will show overdue days. Passing the estimated due date is common, but follow-up timing should always come from your healthcare professional.