IVF Due Date Calculator
IVF pregnancies are the easiest to date precisely — the exact day of fertilization is known. Enter your transfer date and embryo age, or your egg retrieval date, and get an exact due date with the full prenatal milestone timeline.
Your details
Gestational age in an IVF pregnancy is counted the same way as a spontaneous one: fertilization age plus 14 days. A day-5 transfer therefore starts life (on paper) at 2 weeks 5 days.
In a spontaneous pregnancy, the due date formula starts from a proxy (the last period) and assumes an ovulation day nobody witnessed. In an IVF pregnancy, none of that guesswork exists: the embryologists know the hour of fertilization, the exact day the embryo reached day 3, day 5, or day 6 of development, and the exact transfer date. That is why IVF due dates are the most accurate estimates in all of obstetrics — accurate to within about a day, not a week or two.
The formula has one step people consistently get wrong: adding 266 days to the transfer date. That only works for a day-2 transfer. Pregnancy length is counted from fertilization (266 days), and by transfer day the embryo has already been developing for 2 to 6 days. The correct formula is: due date = transfer date + 266 − embryo age in days. For a day-5 blastocyst, that is 261 days from transfer; for a day-3 cleavage-stage embryo, 263 days.
This calculator handles the three standard embryo ages (3, 5, and 6 days), works identically for fresh and frozen transfers (a frozen embryo implants on the same developmental schedule), and offers egg-retrieval dating as an alternative anchor for fresh cycles. The output includes your current gestational age and the same screening milestones — NT window, anatomy scan, glucose screening — computed against the exact date.
How the calculation works
Due date = transfer date + 266 − embryo age. The 266 days run from fertilization to birth; subtracting the embryo age removes the days of development that already happened in the lab.
For egg-retrieval dating, no subtraction is needed: retrieval day is fertilization day, so the due date is retrieval + 266 days. Both methods should agree for a fresh cycle — if they do not, double-check which date the clinic recorded as transfer day.
Frozen transfers follow the same rule regardless of how long the embryo was stored; storage time does not affect developmental age. For frozen embryo transfer cycles, clinics also assign a "cycle day equivalent" so blood test timing lines up with natural cycles — your due date math never needs it, but your clinic's protocol calendar will reference it.
Frequently asked questions
Does a frozen embryo transfer change the due date formula?
No. A frozen day-5 blastocyst transferred in March has the same due date as a fresh day-5 blastocyst transferred the same day. Cryopreservation pauses development completely; the embryo is exactly as many days old on transfer day as it was when frozen. The formula uses only transfer date and embryo age.
What is my gestational age at a day-5 transfer?
Clinicians count pregnancy from the (fictional) last period, which is 14 days before fertilization. So at transfer of a day-5 embryo you are already "2 weeks 5 days pregnant," and at the positive test roughly 9–10 days later you test at about 4 weeks. This is why IVF patients seem to "skip" the first two weeks.
How accurate is an IVF due date compared to a natural one?
Substantially more accurate. Natural-pregnancy dating from last period carries ±1–2 weeks of uncertainty from variable ovulation; an IVF date is known to the day of fertilization, so the EDD is accurate within about a day. Later ultrasound measurements may still shift the official EDD slightly, but the true date never changes.
What if I had a day-6 embryo or a different protocol?
Select day 6 for a day-6 blastocyst — the formula subtracts 6 instead of 5. Day-6 embryos implant on the same schedule but were frozen a day later, so the transfer-to-due-date interval is one day shorter. For less common scenarios (day 7, mosaic transfers, or transfers with a gestational carrier), use retrieval dating, which needs no embryo-age input.
When is my first ultrasound after a positive test?
Clinics typically schedule the first confirmation scan around 6–7 weeks of gestational age (about 3 weeks after a day-5 transfer), looking for a gestational sac, yolk sac, and heartbeat. The dating ultrasound window (8–13w6d) and NT window (11w0d–13w6d) follow the same calendar as any pregnancy, computed from your exact date.
References & sources
- ASRM committee opinion: Due date calculation in pregnancies from ART (guidance on 266-day rule).
- ACOG Committee Opinion 700: Methods for Estimating the Due Date (2017).
- Practice Committee of the ASRM. Definitions of infertility and recurrent pregnancy loss. Fertil Steril. 2013.
- Maheshwari A, et al. Obstetric outcomes after frozen versus fresh embryo transfer. Lancet. 2018 (dating equivalence).