Due Date, Conception & IVF Due Date Worked Examples
Bikash Roy
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Bikash personally verifies every calculator against official standards (WHO, NIH, government data). Online research specialist, SEO strategist, and web developer with 10+ years building accurate digital tools.
Full bio →Seeing the formulas applied to real dates makes the gestational age calculator’s four modes easier to trust. Below are five worked examples covering a standard 28-day cycle, an adjusted cycle length, a reverse due date lookup, an IVF transfer, and a full conception-to-implantation chain.
Example 1 — Standard 28-Day Cycle Due Date
LMP: January 5, 2026. Cycle length: 28 days (default, no adjustment needed).
Due Date = January 5, 2026 + 280 days = October 12, 2026No cycle adjustment applies here since 28 days is the formula’s baseline assumption.
Example 2 — Adjusted Due Date for a Longer Cycle
LMP: February 14, 2026. Cycle length: 33 days.
Base Due Date = February 14, 2026 + 280 days = November 21, 2026
Adjustment = 33 − 28 = +5 days
Adjusted Due Date = November 21, 2026 + 5 days = November 26, 2026A 33-day cycle means ovulation happens later than the day-14 default, so the due date shifts 5 days later than the unadjusted estimate — skipping this step would under-count gestational age by nearly a week at every future check.
Example 3 — Reverse Due Date (Finding LMP from a Known Due Date)
A clinician provides a due date of September 3, 2026, with a standard 28-day cycle.
Estimated LMP = September 3, 2026 − 280 days = November 26, 2025This is useful for reconstructing a timeline when only a due date is on record — see common due date calculation mistakes for why this reverse estimate can differ from an actual recalled LMP if the original due date came from an ultrasound.
Example 4 — Conception and Implantation Window Chain
LMP: June 1, 2026. Cycle length: 30 days.
Base conception estimate = June 1, 2026 + 14 days = June 15, 2026
Cycle adjustment = 30 − 28 = +2 days
Estimated conception date = June 15, 2026 + 2 days = June 17, 2026
Implantation window:
Early estimate = June 17, 2026 + 6 days = June 23, 2026
Late estimate = June 17, 2026 + 10 days = June 27, 2026
Implantation window ≈ June 23 – June 27, 2026Each stage builds on the previous one — the cycle-length adjustment applied to the conception estimate carries forward automatically into the implantation window, since implantation is defined relative to conception, not LMP directly.
Example 5 — IVF Due Date From a Day 5 Transfer
Embryo transfer date: March 3, 2026 (Day 5 blastocyst transfer).
Due Date = March 3, 2026 + 261 days = November 19, 2026Compare this with an equivalent Day 3 transfer from the same retrieval cycle (transfer on March 1, 2026, two days earlier since a Day 3 embryo is transferred two days before a Day 5 blastocyst from the same retrieval):
Due Date = March 1, 2026 + 263 days = November 19, 2026Both land on the identical due date, confirming the two offsets are just different ways of counting from the same retrieval day. See IVF due date: how embryo transfer date sets your due date for the full formula derivation.
Running These Yourself
All five examples above use the exact formulas built into the gestational age calculator — enter any LMP, due date, conception date, or IVF transfer date to reproduce these results instantly, or to check a different date without doing the day-counting by hand.
References & Sources
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