Example Data Table
| Method |
Input date |
Extra input |
Formula summary |
Example due date |
| Last menstrual period |
January 1, 2026 |
28 day cycle |
LMP plus 280 days |
October 8, 2026 |
| Conception date |
January 15, 2026 |
None |
Conception plus 266 days |
October 8, 2026 |
| Day 5 embryo transfer |
January 20, 2026 |
Embryo age 5 |
Transfer plus 261 days |
October 8, 2026 |
| Ultrasound age |
March 5, 2026 |
9 weeks, 0 days |
Scan date plus 217 days |
October 8, 2026 |
Advanced Due Date Planning Guide
A due date is an estimate, not an exact appointment. This calculator helps you compare common dating methods in one place. It can use a last menstrual period, a known conception date, ovulation timing, embryo transfer details, retrieval timing, or an ultrasound measurement. Each method gives a useful planning date. Your clinician may still adjust it after reviewing records, cycle history, scan findings, and medical context.
Why Multiple Methods Matter
The last menstrual period method assumes a regular twenty eight day cycle. Many people have shorter or longer cycles. That is why this tool adjusts the result when you enter another cycle length. Conception and ovulation methods use a shorter interval because pregnancy dating counts from the menstrual start, not from fertilization. Assisted reproduction dates can be more precise because embryo age and procedure date are usually known.
Timeline Results
The result panel gives the estimated due date, pregnancy start, conception estimate, trimester changes, current gestational age, days remaining, and progress percentage. It also adds planning windows for early discussion points and the anatomy scan period. These dates are meant for organization. They should not replace personal medical advice.
Using Results Carefully
Pregnancy length varies naturally. A due date can shift when early ultrasound data conflicts with menstrual dates. The most reliable estimate often depends on how early and accurate the available information is. Keep a copy of the calculation for appointments. Use the CSV download for spreadsheets. Use the PDF download for sharing or printing. Always review final decisions with a qualified care provider.
Formula Used
The calculator uses standard pregnancy dating intervals. For last menstrual period, it adds 280 days, then adjusts for cycle length. For conception or ovulation, it adds 266 days. For embryo transfer, it adds 266 days minus embryo age. For ultrasound, it adds the remaining days in a 280 day pregnancy.
- LMP method: due date = LMP + 280 days + cycle adjustment.
- Cycle adjustment: cycle length minus 28 days.
- Conception method: due date = conception date + 266 days.
- Ovulation method: due date = ovulation date + 266 days.
- Embryo transfer method: due date = transfer date + 266 days - embryo age.
- Ultrasound method: due date = scan date + 280 days - scan age days.
How To Use This Calculator
- Choose the dating method that matches your best information.
- Enter the required date for that method.
- Add cycle length, embryo age, or scan age when needed.
- Press the calculate button.
- Review the result shown above the form.
- Download the CSV or PDF copy when needed.
- Discuss the estimate with a qualified care provider.
FAQs
1. Is this due date exact?
No. A due date is an estimate. Many births happen before or after it. Your provider may adjust the date after reviewing scans, cycle details, and health records.
2. Which method should I choose?
Choose the method based on your most reliable information. Early ultrasound and assisted reproduction dates are often strong references. If unsure, start with your last menstrual period.
3. Why does cycle length change the result?
The standard LMP formula assumes a 28 day cycle. Longer cycles may ovulate later. Shorter cycles may ovulate earlier. The adjustment helps reflect that timing.
4. What is gestational age?
Gestational age counts pregnancy from the estimated first day of the last menstrual period. It is usually about two weeks longer than fetal age.
5. Can I use IVF transfer dates?
Yes. Enter the embryo transfer date and choose day 3 or day 5 embryo age. The tool subtracts embryo age from the standard conception interval.
6. Can ultrasound change my due date?
Yes. Early ultrasound measurements can sometimes update dating. Your provider decides whether a scan should replace menstrual or procedure based estimates.
7. Why are trimester dates included?
Trimester dates help with planning visits, tests, and personal schedules. They are calculated from the estimated pregnancy start date.
8. Should I rely on this for medical decisions?
No. Use this calculator for planning and education only. Always ask a qualified care provider before making medical, testing, or treatment decisions.