Calculator Form
Example Data Table
| Method | Reference Date | Cycle Length | As-Of Date | Estimated Gestational Age | Estimated Due Date |
|---|---|---|---|---|---|
| LMP | 2026-01-15 | 28 | 2026-04-11 | 12 weeks 2 days | 2026-10-22 |
| Conception | 2026-01-29 | 30 | 2026-04-11 | 12 weeks 4 days | 2026-10-22 |
| Due Date | 2026-10-30 | 28 | 2026-04-11 | 11 weeks 1 day | 2026-10-30 |
| IVF Transfer | 2026-02-10 | 28 | 2026-04-11 | 12 weeks 2 days | 2026-10-29 |
Formula Used
This calculator estimates pregnancy duration from four common clinical reference methods.
- LMP method: Due Date = LMP + 280 days + (Cycle Length - 28).
- Conception method: Due Date = Conception Date + 266 days.
- Due date method: LMP = Due Date - 280 days.
- IVF transfer method: Conception Date = Transfer Date - Embryo Age.
- Gestational age: As-Of Date - Estimated LMP.
- Trimester ranges: First: 0-13w6d, Second: 14w0d-27w6d, Third: 28w0d onward.
- Term window: 37 weeks to 42 weeks, relative to the estimated LMP.
These formulas are useful for planning and tracking, but ultrasound dating and clinician review may refine the final timeline.
How to Use This Calculator
- Select the calculation method that matches your available information.
- Enter the related reference date, such as LMP, conception, due date, or IVF transfer date.
- Choose the as-of date to measure pregnancy duration on a specific day.
- Adjust cycle length when using LMP or conception if your cycle differs from 28 days.
- Select embryo age only when using the IVF transfer method.
- Click Calculate Duration to show results above the form.
- Review gestational age, trimester, due date, term window, milestone timing, and progress chart.
- Use the CSV or PDF buttons to save the calculated summary.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates gestational age, due date, trimester, conception timing, term window, and remaining time to 40 weeks using several common date-entry methods.
2. Which method is usually best?
LMP is commonly used first. Conception or IVF dates can be more precise when known. Ultrasound dating may later adjust the estimated due date.
3. Why does cycle length matter?
Longer or shorter cycles can shift estimated ovulation and slightly change the due date when calculations start from LMP or conception assumptions.
4. Can I use this for IVF pregnancies?
Yes. Choose the IVF transfer method and select the embryo age. The calculator then estimates conception, due date, and gestational age accordingly.
5. Is the due date exact?
No. It is an estimate. Many pregnancies deliver before or after the calculated date, which is why the term window is also shown.
6. What if I am already past the due date?
The calculator will show how many days past due you are. That information should be reviewed with your maternity care professional.
7. Can this replace medical advice?
No. It is a planning and tracking tool. For diagnosis, dating confirmation, or care decisions, rely on your clinician and ultrasound findings.
8. Are my dates stored permanently?
This page processes the values you submit for calculation. Any long-term storage depends on your own server setup and logging configuration.