How the IVF due date is calculated
After an in vitro fertilization (IVF) transfer, the date of conception is known to the day, so the due date can be dated from the embryo's age instead of from a last period. The calculation is short. For a day-5 embryo, add 261 calendar days to the transfer date. For a day-3 embryo, add 263 days. Those two numbers come from the usual 280-day pregnancy counted from the last period: a day-5 embryo is already counted as 19 days old on transfer day (280 − 19 = 261), and a day-3 embryo as 17 days old (280 − 17 = 263). The American College of Obstetricians and Gynecologists (ACOG) describes dating an IVF pregnancy from the embryo's age and transfer date in its Committee Opinion on methods for estimating the due date.
The calculator also shows your gestational age on transfer day. A day-3 transfer is 2 weeks 3 days (2w3d) and a day-5 transfer is 2 weeks 5 days (2w5d). Gestational age is counted as if the pregnancy had started on the first day of a last period about two weeks before conception, which is why a transfer that happens days after fertilization is already two weeks old on paper.
Worked example
Suppose the embryo transfer is on Thu 15 Jan 2026. With a day-5 embryo the estimated due date is 15 January plus 261 days, which is Sat 3 Oct 2026, and the gestational age on transfer day is 2 weeks 5 days. With a day-3 embryo, the same transfer date gives an estimated due date of Mon 5 Oct 2026 and a gestational age of 2 weeks 3 days.
Notice that the two due dates differ by two days. A day-5 embryo has had two more days of development before transfer than a day-3 embryo, so its due date comes two days earlier for the same transfer date. The nominal gestational start, the date you would count as the first day of a last period, works out to Sat 27 Dec 2025 for the day-5 case and Mon 29 Dec 2025 for the day-3 case.
Fresh and frozen transfers
The arithmetic is the same for a fresh or a frozen embryo transfer, as long as you know the embryo's age on the day it was transferred. The age counts from fertilization, so a day-5 embryo that was frozen and thawed is still a day-5 embryo for dating. Enter the transfer date and the embryo age exactly as your clinic reports them. This calculator does not attempt to date a pregnancy from the date of egg retrieval, from a hormone schedule or from the start of medication.
If you do not know the embryo age
This calculator offers day-3 and day-5 transfers only. If the embryo age is unknown, the transfer was on another day, or the clinic did not state it, ask your clinic which dates they use. Do not guess: a wrong day shifts the answer by about two days per step. Your clinic's confirmed dating and any ultrasound redating should always replace a calculated date. If your due date came from a last period instead, use the pregnancy due date calculator. If you already have a due date and want to see the dates behind it, use the reverse due date calculator, which works backward and does not use embryo age.
What the date means
An estimated due date is a point in the middle of a window of weeks, not a prediction of the day a baby will arrive. Few babies are born on that exact day. The date also does not describe the health of the pregnancy, and it does not replace the dating your care team records. If anything on this page differs from what your clinic told you, follow your clinic.
You can see all of the pregnancy and cycle tools on the Fitness & Health calculators page, including the ovulation calculator for natural cycles.
Frequently asked questions
How do I calculate my due date after a day-5 transfer?
Add 261 days to the transfer date. For a transfer on Thu 15 Jan 2026 that gives Sat 3 Oct 2026.
How do I calculate my due date after a day-3 transfer?
Add 263 days to the transfer date. For the same transfer date that gives Mon 5 Oct 2026.
Does it matter whether the transfer was fresh or frozen?
No. What matters is the embryo's age on the day of transfer, which the clinic can tell you.
Why is my gestational age already 2 weeks on transfer day?
Gestational age counts from the first day of a last period, about two weeks before conception. The embryo's own age is added to those two weeks.
Can I use this for a day-6 embryo or an unknown embryo age?
Not here. This version covers day-3 and day-5 transfers. Ask your clinic for the dating they use in other cases.
Sources and limits of this page
The offsets follow ACOG, Committee Opinion No. 700: Methods for Estimating the Due Date (2017). This page is educational information, not medical advice, and it has not been reviewed by a clinician. Dates are calculated in your browser on the calendar only, with no time zone, and nothing you enter is saved or sent.