How an IVF due date is calculated
Why IVF dates are exact
With IVF, the day the egg was fertilised is known. That makes the due date more exact than one based on a period.
Step by step
- Find your transfer date.
- Check whether the embryo was 3 or 5 days old at transfer.
- Add 261 days (day 5) or 263 days (day 3).
Example: a day-5 transfer on 1 March 2026 gives a due date of 17 November 2026. A day-3 transfer on the same day gives 19 November 2026.
Where the numbers come from
A pregnancy is counted as 280 days from an “LMP-equivalent” start. A day-5 embryo is like day 19 of that count (280 − 19 = 261), a day-3 embryo like day 17 (280 − 17 = 263). Try the IVF due date calculator.
Your pregnancy week on transfer day
The same count gives your week: on the day of a day-5 transfer you are 2 weeks 5 days pregnant (19 days), and on the day of a day-3 transfer 2 weeks 3 days (17 days).
Sources
- ACOG Committee Opinion 700: Methods for Estimating the Due Date · checked October 24, 2026