IVF Due Date Calculator
Enter your transfer date and whether it was a day 3 embryo or a day 5 blastocyst. We work out your due date and where you are today.
This calculator gives general estimates for information only. It is not medical advice and does not replace a consultation with a doctor or other qualified health professional.
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The formula
Due date = transfer date + 266 days - embryo age (3 or 5). Equivalent last-period date = transfer date - (embryo age + 14 days).
Why IVF dating is more exact
With IVF the day of fertilisation is known, so there is less guesswork than with a last period date. A day 5 blastocyst transfer means the embryo is 5 days old at transfer, so conception is counted as 5 days earlier.
The method
We take the transfer date, subtract the embryo age to find the equivalent conception date, and add 266 days. For a day 5 transfer on 1 March 2026 that gives a due date of 17 November 2026.
Check with your clinic
Your fertility clinic will give you an official due date and scan schedule. If it differs by a day, follow the clinic, because they know your protocol.
Examples to check
Type these into the calculator above to see how it behaves. Every result below was produced by the same calculator code that runs on this page.
| What you enter | What you get |
|---|---|
| IVF transfer date; Embryo transfer date: 2026-03-01; Day 5 blastocyst | Estimated due date: Tuesday, November 17, 2026 |
| IVF transfer date; Embryo transfer date: 2026-05-20; Day 3 embryo | Estimated due date: Sunday, February 7, 2027 |
| IVF transfer date; Embryo transfer date: 2026-08-11; Day 5 blastocyst | Estimated due date: Thursday, April 29, 2027 |
IVF Due Date Calculator: frequently asked questions
What is the difference between a day 3 and a day 5 transfer?
The number refers to how many days after fertilisation the embryo was transferred. A day 5 embryo is a blastocyst, which is more developed.
How accurate is an estimated due date?
Only about 4 in 100 babies arrive on the due date. Most are born within two weeks either side. Treat the date as the middle of a window, and follow your midwife or doctor, who may adjust it after a scan.
Why do doctors count from the last period if conception happens two weeks later?
Because most people remember the start of their last period but not the exact day of conception. Pregnancy weeks are counted from that date, so you are already "two weeks pregnant" at conception.
Can I rely on this result as medical advice?
No. It is a general estimate for information only. It cannot replace a check-up, and your doctor can interpret the numbers for your own situation.
Is what I enter in this calculator saved or sent anywhere?
No. The calculation runs in your browser, so what you enter is not sent to our servers. We only count, anonymously, whether a tool ran successfully.
Is this calculator free to use?
Yes. It is free, needs no sign-up and has no usage limit.
Last reviewed: October 3, 2026