IVF Due Date Calculator

The IVF Due Date Calculator estimates your pregnancy due date from the date of your embryo transfer. Because an IVF cycle pins down the exact moment of fertilization and the precise age of the embryo, an IVF due date is one of the most accurate estimates in all of obstetrics — there is no guesswork about when conception happened. This tool works for a Day-3 cleavage-stage transfer or a Day-5 / Day-6 blastocyst transfer, fresh or frozen (FET), and also shows your egg-retrieval date, equivalent LMP, how many weeks pregnant you are today, and every key pregnancy milestone with real calendar dates.

How the IVF Due Date Is Calculated

A full-term pregnancy lasts about 266 days from conception (or 280 days / 40 weeks from the last menstrual period). In IVF, "conception" is the day of egg retrieval and fertilization, and the embryo's age at transfer is known exactly. So the due date is found by counting forward from your transfer date and subtracting the embryo's age:

This gives a clean rule for each transfer type:

• Day-3 transfer: Due Date = Transfer Date + 263 days
• Day-5 transfer (blastocyst): Due Date = Transfer Date + 261 days
• Day-6 transfer (blastocyst): Due Date = Transfer Date + 260 days

Why an IVF Due Date Is More Accurate

A standard pregnancy due date uses Naegele's rule, which counts 280 days from the first day of the last menstrual period and assumes ovulation happened on a textbook day 14. In reality, ovulation timing varies from cycle to cycle, so a normal due date can be off by several days. With IVF, the laboratory records the exact date of fertilization and watches the embryo develop, so its age is certain. That removes the biggest source of error and makes the IVF due date a gold-standard estimate.

Day-3 vs Day-5 Transfer: What Changes?

The only thing that changes is the embryo's age, which is subtracted from 266. A Day-5 blastocyst is two days older than a Day-3 embryo, so for the same transfer date, a Day-5 due date falls two days earlier than a Day-3 due date. The choice of transfer day is a clinical decision based on embryo quality and your treatment plan — it does not change how the due date is calculated, only the number you subtract.

Does a Frozen Embryo Transfer (FET) Change Anything?

No. The calculation depends only on the developmental age of the embryo at the moment of transfer, never on how long it spent frozen. A frozen Day-5 blastocyst and a fresh Day-5 blastocyst are dated with exactly the same formula once you know the transfer date. This is why this calculator asks for the embryo age (Day 3, 5, or 6) rather than whether it was a fresh or frozen cycle.

How Many Weeks Pregnant Am I After Transfer?

Gestational age is counted from the equivalent LMP, about 14 days before conception. So on the day of your transfer you are already a couple of weeks "pregnant" on paper:

Pregnancy Milestones to Watch

• ~6 weeks: A heartbeat can often be seen on an early ultrasound.
• ~11–13 weeks: First-trimester / NT screening scan.
• 13 weeks: End of the first trimester; miscarriage risk drops sharply.
• ~20 weeks: Anatomy scan; the baby's sex is often visible.
• 24 weeks: Viability — survival outside the womb becomes possible with intensive care.
• 37 weeks: Full term begins.
• 40 weeks: Your estimated due date.
• 42 weeks: Post-term; most providers will deliver by now.

Will My Baby Arrive Exactly on the Due Date?

Almost certainly not — and that is completely normal. Only about 1 in 20 babies is born on the estimated due date. A pregnancy is considered full term anywhere from 37 to 42 weeks, a five-week window. The due date is best thought of as the center of that window rather than a deadline.

How to Use This Calculator

1. Enter your transfer date: The day your embryo was transferred to the uterus.
2. Choose the embryo age: Day-3 cleavage, or Day-5 / Day-6 blastocyst. Fresh and frozen use the same setting.
3. Click Calculate: Your due date, key dates, and milestone timeline appear instantly.
4. Review your timeline: See how many weeks pregnant you are today and every milestone with a real date.

Frequently Asked Questions

How is an IVF due date calculated?

A full-term pregnancy lasts 266 days from conception. In IVF the embryo's age is known exactly, so the due date is the transfer date plus 266 days minus the embryo age. A Day-5 blastocyst transfer adds 261 days, while a Day-3 transfer adds 263 days.

Is an IVF due date more accurate than a normal due date?

Yes. A standard due date estimates the conception date from the last menstrual period, which can be off by several days because ovulation timing varies. With IVF the exact date of fertilization and the embryo's age are known, so the due date is one of the most precise estimates possible.

What is the difference between a Day-3 and a Day-5 transfer due date?

The embryo age is subtracted from 266 days. A Day-5 blastocyst is older at transfer, so its due date is the transfer date plus 261 days. A Day-3 embryo is younger, so its due date is the transfer date plus 263 days. For the same transfer date, a Day-5 due date is two days earlier than a Day-3 due date.

Does a frozen embryo transfer (FET) change the due date?

No. The calculation depends only on the developmental age of the embryo at transfer, not on how long it was frozen. A frozen Day-5 blastocyst and a fresh Day-5 blastocyst use exactly the same formula once the transfer date is known.

How many weeks pregnant am I after a Day-5 transfer?

On the day of a Day-5 blastocyst transfer you are considered 2 weeks and 5 days pregnant by obstetric dating, because gestational age is counted from the equivalent last menstrual period, about 14 days before conception. A Day-3 transfer day counts as 2 weeks and 3 days.

Will my baby be born exactly on the due date?

Probably not. The due date is the 40-week mark, but only about 1 in 20 babies arrives on it. A pregnancy is considered full term from 37 to 42 weeks, so any birth in that five-week window is normal.

Additional Resources

• In Vitro Fertilisation - Wikipedia
• Estimated Date of Delivery - Wikipedia

This calculator provides estimates for general information only and is not a substitute for professional medical advice. Your fertility clinic or obstetrician will confirm your official due date, usually with an early dating ultrasound.