About the IVF Due Date Calculator
This IVF due date calculator works out your estimated due date from the date of your embryo transfer and the age of the embryo when it was transferred. Because the exact day of fertilization is known in IVF, the due date is more precise than one estimated from a last menstrual period, and it is the date your clinic and obstetrician will typically use.
It works for fresh and frozen embryo transfers (FET) of day-3 cleavage-stage embryos, day-5 or day-6 blastocysts, and for dating from egg retrieval or IUI. Along with the due date it shows the equivalent “last period” date, how many weeks and days pregnant you are on any date you choose, the usual beta hCG blood test date and key milestones.
Pregnancy weeks are counted as if you had a last period two weeks before conception, so on the day of a 5-day blastocyst transfer you are already considered 2 weeks and 5 days pregnant. Only about 4–5% of babies arrive exactly on their due date; most are born within two weeks either side.
How to use the ivf due date calculator
- 1Enter the date of your embryo transfer (fresh or frozen).
- 2Choose the embryo age: 3-day, 5-day or 6-day — or egg retrieval/IUI date.
- 3Optionally set a date to see how many weeks pregnant you will be then.
- 4Read your due date, equivalent LMP and the beta hCG test date.
- 5Use the milestone table to plan scans and appointments.
Formula and method
A pregnancy lasts on average 266 days (38 weeks) from fertilization, or 280 days (40 weeks) from an assumed last menstrual period two weeks before fertilization. In IVF the fertilization date is known: it is the transfer date minus the embryo’s age in days. So a 5-day blastocyst due date is the transfer date plus 261 days, a 3-day embryo transfer date plus 263 days, and a 6-day blastocyst plus 260 days.
The same rule applies to frozen transfers, because the embryo’s developmental age — not the date it was created — is what counts. Gestational age on any date is the number of days since the equivalent LMP, shown in weeks and days. The beta test date shown is 14 days after fertilization (4 weeks of pregnancy), which is when most clinics check hCG.
- T
- Embryo transfer date
- A
- Embryo age at transfer in days (3, 5 or 6; 0 for retrieval/IUI)
- EDD
- Estimated due date = T + 266 − A
Worked examples
5-day blastocyst transferred 10 September 2026
Fertilization was 5 days before transfer, on 5 September. Adding 266 days gives a due date of 29 May 2027, equivalent to an LMP of 22 August 2026. On 29 October 2026 you would be 9 weeks 5 days pregnant with 212 days to go.
3-day embryo transfer
A day-3 embryo transferred on 3 November was fertilized on 31 October, so the due date is 263 days after transfer: 24 July 2027. By 1 December you would be 6 weeks 3 days — about the time of a first heartbeat scan.
6-day frozen blastocyst
A day-6 blastocyst transferred on 15 January 2027 gives a due date 260 days later, on 2 October 2027. On 1 June 2027 that pregnancy would be 22 weeks 3 days, in the second trimester.
Frequently asked questions
How do you calculate a due date after a 5-day embryo transfer?+
Add 261 days to the transfer date (266 days from fertilization minus the 5 days the embryo grew in the lab). For example, a 5-day transfer on 1 March gives a due date around 17 November.
Is the IVF due date more accurate than a natural pregnancy due date?+
The dating is more precise because the fertilization date is known exactly, so there is no uncertainty about ovulation. Babies still arrive naturally over a range, with most born between 37 and 42 weeks.
How many weeks pregnant am I on the day of my embryo transfer?+
By standard dating you are 2 weeks plus the embryo’s age: 2 weeks 5 days on the day of a 5-day blastocyst transfer, or 2 weeks 3 days for a 3-day transfer.
Does a frozen embryo transfer change the due date calculation?+
No. For a frozen embryo transfer you use the transfer date and the embryo’s age at freezing (for example, a day-5 blastocyst), exactly as for a fresh transfer. The years spent frozen do not count.
When is the beta hCG test after IVF?+
Most clinics schedule the first blood pregnancy test about 9–11 days after a blastocyst transfer and 11–14 days after a day-3 transfer. Follow your own clinic’s date, as protocols differ.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.