IVF Due Date Calculator
Calculate a due date from a day-3, day-5 or day-6 embryo transfer.
About the IVF Due Date Calculator
With IVF the date of fertilisation is known exactly, so the due date is more precise than one based on a last period. Choose the embryo's age at transfer and enter the transfer date; the calculator gives the estimated due date, the equivalent last-period date that clinics and apps use for counting weeks, and when a blood test is usually done.
A day-5 embryo is 5 days past fertilisation at transfer, so the due date is the transfer date + 261 days (266 − 5); for a day-3 embryo add 263 days. ACOG recommends dating IVF pregnancies this way.
The formula
Due date = transfer date + 266 − embryo age (days)
- 266
- average days from fertilisation to birth
- embryo age
- 3, 5 or 6 days at transfer
Worked example
Day-5 blastocyst transferred on 10 June 2026
- 266 − 5 = 261 days after transfer
- Estimated due date: 26 February 2027
- Equivalent last-period date: 22 May 2026, so pregnancy weeks count from then
Things to keep in mind
- Only about 1 in 20 babies arrives on the due date itself; most come within two weeks either side.
- Your clinic's dating, often confirmed by an early scan, takes priority.
Questions people ask
Why 266 days?
That's the average from conception to birth (280 from the last period).
Frozen transfers?
Same calculation, using the embryo's age at transfer.
How many weeks pregnant am I at transfer?
For a day-5 transfer, 2 weeks 5 days, because weeks are counted from the equivalent last-period date.