Calculator Inputs
Example Data Table
| Method | Input Example | Extra Setting | Estimated Result |
|---|---|---|---|
| Last menstrual period | January 1, 2026 | 28 day cycle | October 8, 2026 |
| Conception date | January 15, 2026 | No adjustment | October 8, 2026 |
| Day 5 transfer | January 20, 2026 | Embryo age 5 days | October 8, 2026 |
| Ultrasound | March 5, 2026 | 9 weeks 0 days | October 8, 2026 |
Formula Used
Last menstrual period: Due date = LMP date + 280 days + cycle adjustment.
Cycle adjustment: Cycle adjustment = average cycle length - 28 days.
Conception: Due date = conception date + 266 days.
Embryo transfer: Due date = transfer date + 266 days - embryo age.
Ultrasound: Due date = scan date + 280 days - scan gestational age in days.
Gestational age today: Gestational age = 280 days - days remaining until due date.
How to Use This Calculator
- Select the dating method that matches your best information.
- Enter the needed date fields for that method.
- Add cycle length when using the last period method.
- Use embryo age when selecting the transfer method.
- Enter scan weeks and days for ultrasound dating.
- Press Calculate to view results above the form.
- Use CSV or PDF buttons to save your results.
Due Date Planning Guide
Why Due Date Estimates Matter
A due date estimate gives a practical starting point for pregnancy planning. It is not a promise. Babies can arrive before or after the calculated date. This calculator helps compare several common dating methods in one place.
Last Period Method
The last menstrual period method uses the first day of the last period. It adds 280 days. A cycle adjustment is added when the cycle is longer or shorter than 28 days. This is useful when ovulation is not exactly mid cycle.
Conception Method
The conception method starts from the likely fertilization date. It adds 266 days. This method can fit users who tracked ovulation, used fertility charts, or know the timing with better confidence.
Transfer Method
The transfer method supports assisted reproduction planning. It subtracts the embryo age from 266 days after transfer. A day five embryo therefore leaves fewer days until the estimated delivery date.
Ultrasound Method
The ultrasound method uses the scan date and gestational age recorded during that scan. Earlier scans usually give a stronger dating estimate than later scans, because early growth varies less.
Result Details
After calculation, the tool shows gestational age today. It also shows the current trimester, days remaining, estimated conception date, and useful milestones. These dates can support appointment planning, work planning, and family preparation.
Medical Review
Results should be reviewed with a qualified clinician. Medical history, irregular cycles, scan quality, and individual pregnancy factors can change the final date used in care.
Planning Notes
Use the result as a planning estimate, not a diagnosis. Keep a record of the input method used. This makes the number easier to explain during a visit. When two methods disagree, clinicians often compare cycle history, early ultrasound findings, and treatment records.
Appointment Support
A due date also helps estimate pregnancy weeks. Many appointments, screening windows, and preparation tasks depend on gestational age. The calculator lists milestone dates to make those windows easier to see. It can also export a record for personal files.
Best Results
For best results, enter dates carefully. Use the earliest reliable information available. Update the estimate after a clinician confirms a dating scan or adjusts the care plan. Always seek urgent care for bleeding, severe pain, reduced fetal movement, or symptoms that worry you. This tool supports clear notes, simple comparisons, and calm preparation before the next prenatal appointment.
FAQs
1. Is this due date exact?
No. It is an estimate. Many babies arrive before or after the calculated date. A clinician may adjust it after reviewing cycle history, ultrasound findings, or treatment records.
2. Which method is best?
The best method depends on your information. Early ultrasound dating is often useful. IVF transfer dates can be very specific. LMP dating works better when cycles are regular.
3. Why does cycle length matter?
Cycle length affects estimated ovulation timing. Longer cycles may move the due date later. Shorter cycles may move it earlier. The calculator adjusts from a 28 day cycle.
4. What does gestational age mean?
Gestational age is pregnancy age counted from the estimated pregnancy start date. It is usually about two weeks more than fetal age from conception.
5. How is IVF transfer calculated?
The calculator adds 266 days to the transfer date, then subtracts embryo age. A day five transfer uses fewer remaining days than a day three transfer.
6. Can I export the result?
Yes. Use the CSV button for spreadsheet records. Use the PDF button for a simple printable summary of dates, milestones, and calculation notes.
7. Should I use this for medical decisions?
No. Use it for education and planning only. Always confirm pregnancy dating, symptoms, and care decisions with a qualified healthcare professional.
8. Why do different methods give different dates?
Each method starts from different information. Period dates, ovulation timing, embryo age, and scan measurements can vary. Your clinician can choose the best final date.