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IVF Due Date Calculator
Your embryo transfer
Example: transfer Jan 15, 2026, 5-day embryo → due Oct 3, 2026; conception-equivalent Jan 10, 2026.
Behind the numbers
How your IVF due date is calculated
A normal pregnancy is counted as 280 days (40 weeks) from the first day of the last period, which is the same as 266 days from conception. In IVF the transfer date is known exactly, so the due date is worked out backwards from it: the embryo is already a few days old at transfer, so those days are subtracted from 266. A 5-day embryo (blastocyst) means the due date is the transfer date plus 261 days; a 3-day embryo means the transfer date plus 263 days. The "conception-equivalent" date is the date a natural conception would have happened to give the same due date — it is simply the due date minus 266 days.
Due date = transfer date + (266 − embryo age in days). For a 5-day transfer on January 15, 2026: 266 − 5 = 261 days, so January 15, 2026 + 261 days = October 3, 2026. The conception-equivalent date is October 3, 2026 − 266 days = January 10, 2026. For a 3-day transfer the same date gives 266 − 3 = 263 days, so the due date is October 5, 2026 — just two days later. At transfer, a 5-day embryo is already 5 + 14 = 19 days, or 2 weeks and 5 days, into the pregnancy as doctors count it.
Examples
Example due dates
| Transfer date | Embryo | Due date | Conception-equivalent |
|---|---|---|---|
| January 15, 2026 | 5-day | October 3, 2026 | January 10, 2026 |
| January 15, 2026 | 3-day | October 5, 2026 | January 12, 2026 |
| April 10, 2026 | 5-day | December 27, 2026 | April 5, 2026 |
| July 1, 2026 | 3-day | March 21, 2027 | June 28, 2026 |
Tips
Only about 1 in 20 babies arrives exactly on the due date — most come within two weeks before or after it, so treat the date as the middle of a window.
Your clinic's ultrasound dating in the first trimester is more accurate than any date calculation, and your doctor may move the due date slightly after the first scan.
The difference between a 3-day and a 5-day transfer is only 2 days, so do not worry if you are unsure which one you had — ask your clinic to confirm.
Keep the conception-equivalent date handy: some forms and apps ask for a "last period" or "conception" date, and this is the date to use.
Good to know
Frequently asked questions
Why is the due date 266 days from conception, not 280?
Doctors count pregnancy as 280 days from the last period, but conception happens about 14 days after that. 280 − 14 = 266 days from conception, which is the number used for IVF because the transfer date is known.
Does a 3-day or 5-day embryo change the due date much?
By only 2 days. A 5-day transfer gives a due date 261 days after transfer; a 3-day transfer gives 263 days after transfer.
What if my transfer was a frozen embryo?
The same formula applies. The embryo's age in days (3 or 5) is what matters, not whether it was fresh or frozen.
Is this due date final?
No. It is an estimate for planning. Your doctor may adjust it after the first ultrasound, which measures the baby directly. This calculator is not medical advice — follow your clinic's guidance.