Estimate pregnancy due dates from LMP, conception, ultrasound dating or IVF transfer, with date-safe gestational progress and a clear milestone timeline.
01 / PREGNANCY DATING
Estimate pregnancy dates from an established calendar method. A due date is a reference point, never a guaranteed delivery day.
| Method | Dating calculation | Main limitation |
|---|---|---|
| LMP | Period + 280 days + cycle adjustment | Approximate for irregular cycles |
| Conception | Estimated fertilization + 266 days | Conception timing may be uncertain |
| Ultrasound | Scan + (280 − reported gestational days) | Requires clinician-reported dating |
| IVF | Transfer + (266 − embryo age) | Use the fertility clinic’s records |
Clinical ultrasound dating may take precedence depending on medical circumstances, scan timing and the clinician’s assessment. Do not average competing estimates; confirm which established due date should guide care.
02 / YOUR ESTIMATED TIMELINE
Calendar-based gestational age at the selected reference date, if the pregnancy is ongoing. This does not establish pregnancy status or a delivery date.
Due date = LMP + 280 days + (cycle length − 28). Cycle adjustment approximates ovulation timing; irregular cycles need individualized clinical dating.
Trimester and 37/40/42-week markers are educational dating conventions, not medical diagnoses. The LMP-equivalent dating start is not an observed conception date.
Confirm clinical pregnancy dating and ultrasound interpretation with a healthcare professional. Dates do not confirm pregnancy, establish whether it is ongoing, or predict the exact delivery day. Inputs stay in browser memory.
Enter your values locally; no inputs are uploaded.
Check validation feedback before reviewing the browser-generated result.
Review the explanation, copy supported outputs or reset the workspace.
Choose the dating method and enter its reported date and relevant details. Review the educational due date, progress reference and milestones; confirm clinical dating with your healthcare professional.
Compare four established pregnancy-dating methods without averaging them. Date-only arithmetic preserves leap days and timezone boundaries; reference-date explanations and a milestone marker separate calendar progress from pregnancy status.
Pregnancy dates, ultrasound dating details and IVF embryo age are processed in browser memory. These inputs are not uploaded, saved to an account or sent to an external calculation service. Copying shares only the result you choose to place on your clipboard.
The estimate is the first day of the last menstrual period plus 280 days plus cycle length minus 28 days. A usual cycle of 28 days adds 280 days; 32 days adds 284. Cycle adjustment is an approximation, especially with irregular cycles.
Estimated conception plus 266 calendar days gives the conventional due-date estimate. This does not establish when fertilization actually happened or predict an exact delivery day.
Enter the scan date and the clinician-reported gestational age in completed weeks and additional days. The calculator adds 280 minus that gestational age in days. It calculates from an entered estimate and never interprets medical images.
Yes. Add 266 minus the embryo age in days: 263 days for a day-3 transfer, 261 for day 5 and 260 for day 6. Transfer is not conception; follow your fertility clinic’s established dates.
Date strings are validated as calendar dates and normalized to UTC calendar-day numbers before addition or subtraction. Weekday and date formatting explicitly use UTC, avoiding local daylight-saving timestamp differences.
No. The timeline uses educational dating conventions: trimester references at 14 and 28 weeks, and milestones at 37, 40 and 42 weeks. Progress is withheld outside the modeled range. Clinical dating, monitoring and ultrasound interpretation belong with a healthcare professional.