IVF Due Date Calculator

IVF pregnancies are dated from embryo age at transfer plus time since transfer. A common formula: due date = transfer date + (266 − embryo age in days), where 266 days represents gestation from conception to term in calendar math.

Day-5 blastocyst transfers are most common in fresh and frozen cycles; day-3 cleavage-stage embryos and day-6 expanded blastocysts use the same formula with a different embryo age input. Your fertility clinic may adjust dating after early ultrasound.

Example: day-5 embryo transferred July 15, 2026 → due date about May 1, 2027 (266 − 5 = 261 days after transfer). Confirm with your reproductive endocrinologist.

IVF dating is usually more precise than dating a spontaneous pregnancy, because the conception date is known to the day rather than estimated from a last menstrual period. That is why clinics rarely revise an IVF due date after the first-trimester scan, while LMP-based dates are often adjusted by several days.

Clinics also express the same date as a gestational age. Transfer day of a day-5 blastocyst corresponds to 2 weeks and 5 days of gestational age, so counting forward from transfer in the familiar “weeks pregnant” format starts near 2w5d rather than zero — useful when comparing this result with a pregnancy tracker.

The 266-day figure is gestation measured from conception, whereas the 280 days behind the standard 40-week due date is measured from the last menstrual period. The 14-day difference is why an IVF calculation and an LMP calculation are not interchangeable formulas.

Day-3 cleavage embryos and day-6 expanded blastocysts use the same formula with a different embryo age, and frozen transfers follow the transfer date rather than the date the embryos were created — an embryo frozen years earlier is still dated from the day it was transferred.

Treat any calculated date as an estimate: only about 4% of births occur on the due date, and the American College of Obstetricians and Gynecologists defines full term as 39 weeks 0 days through 40 weeks 6 days. Your reproductive endocrinologist sets the official date that drives monitoring appointments; this is calendar math, not medical advice.

Frozen embryo transfers may use a different dating offset than fresh cycles — follow the embryology lab and your RE clinic for the official EDD that drives monitoring appointments.