IVF Due Date Calculator
Because IVF fixes the conception point precisely, due-date estimation is more exact than for naturally conceived pregnancies. The estimated due date equals the embryo transfer date plus 266 days (the post-conception term) minus the embryo's age in days at transfer. A day-5 blastocyst transfer adds 261 days; a day-3 transfer adds 263 days. Enter the transfer date and the embryo age and this calculator returns the estimated due date and the current gestational age. It is general information; your clinic sets the official dating, often with an early ultrasound.
IVF due date formula
Days added = 266 - embryo age at transfer
Due date = transfer date + days added
Gestational age = 280 - days from now to due date, in weeks
Day-5 transfer adds 261 days; day-3 transfer adds 263 days
The 266-day post-conception term equals the 280-day last-menstrual-period term minus 14 days. Subtracting embryo age aligns the count to the conception equivalent.
IVF dating context
- IVF dating is precise because the conception point is known.
- A full term is about 280 days from the last menstrual period, or 266 from conception.
- Blastocyst (day-5) transfers add 261 days; cleavage-stage (day-3) transfers add 263.
- Only about one birth in twenty falls on the exact estimated date.
- This tool is general information and not medical advice.
IVF due date: frequently asked questions
How is an IVF due date calculated?
With IVF the conception date is known precisely, so dating is more exact than from a last menstrual period. The estimated due date equals the transfer date plus 266 days (the post-conception term) minus the embryo's age in days at transfer. A day-5 blastocyst transfer therefore adds 261 days, and a day-3 transfer adds 263 days.
Why 266 days instead of 280?
A full-term pregnancy is about 280 days (40 weeks) when dated from the last menstrual period, which is roughly 14 days before conception. Because IVF dates from a known conception or egg-retrieval point, the calculation uses 266 days, which is 280 minus those 14 days, then adjusts for embryo age at transfer.
What embryo age should I enter?
Enter the day on which the embryo was transferred relative to fertilization: 3 for a day-3 (cleavage stage) transfer or 5 for a day-5 (blastocyst) transfer. The calculator subtracts that from 266 days so the count runs from the equivalent conception point.
How accurate is the IVF due date?
Because conception timing is known, IVF due dates are typically more precise than naturally conceived estimates. Even so, only about one in twenty babies arrives exactly on the estimated date, and term spans several weeks. Your clinic confirms dating, often with an early ultrasound.
Is this calculator medical advice?
No. It performs calendar arithmetic for general information. Your fertility clinic and obstetric provider set your official dating and care plan. Always rely on your care team for clinical decisions.
Official sources
- U.S. National Library of Medicine, MedlinePlus: due date and gestational age.
- U.S. Centers for Disease Control and Prevention: Reproductive Health.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.