What this calculator does
A due date calculated from a last menstrual period assumes ovulation happened around day 14 of a fairly regular cycle. IVF and frozen embryo transfer pregnancies do not fit that model: the embryo's age on the day it was placed in the uterus is already known precisely, because it was grown and graded in a laboratory, so the due date is worked out from the transfer date instead.
This IVF due date calculator adds a fixed number of days to the transfer date depending on whether the embryo was a Day 3 (cleavage-stage) or Day 5 (blastocyst) transfer. It gives the same estimate a standard 280-day pregnancy would reach if the embryo's exact conceptional age is counted back correctly, which is why the offset for a Day 5 transfer is shorter than for a Day 3 one.
The formula
A full-term pregnancy is conventionally dated at 280 days from the last menstrual period, with ovulation and fertilisation assumed on day 14. A Day 5 embryo is already 5 days past fertilisation at transfer, so only 261 days remain to reach that 280-day mark (280 minus 14 minus 5). A Day 3 embryo is 3 days past fertilisation, so 263 days remain (280 minus 14 minus 3).
| Term | Meaning |
|---|---|
| Day 3 transfer | A cleavage-stage embryo, transferred three days after fertilisation. |
| Day 5 transfer | A blastocyst-stage embryo, transferred five days after fertilisation; the more common choice in current practice. |
| Gestational age | Pregnancy age counted from the last menstrual period convention, not from the actual date of fertilisation. |
The inputs explained
| Field | What to enter |
|---|---|
| Embryo transfer date | The date the embryo was placed in the uterus, from the clinic's records. |
| Transfer day | Whether it was a Day 3 (cleavage-stage) or Day 5 (blastocyst) embryo. This is on the transfer paperwork if unsure. |
When to use it
After a fresh or frozen transfer
Both fresh IVF cycles and frozen embryo transfer (FET) cycles use the same offset from the actual transfer date, since what matters is the embryo's age on that day, not how the cycle was prepared.
Comparing to a clinic's own dating
Clinics typically confirm and sometimes slightly adjust the due date at the first ultrasound, based on measured growth. This calculator gives the starting estimate that dating is checked against.
Working out gestational age today
Because the transfer date fixes the embryo's age precisely, gestational age today can be read off directly rather than estimated, which is one advantage IVF dating has over last-menstrual-period dating.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the due date shifts between a Day 3 and Day 5 transfer
The same embryo transfer date, worked out for a Day 3 and a Day 5 transfer.
| Transfer day | Estimated due date | Days from transfer to due date |
|---|---|---|
| Day 3 | 19 Nov 2026 | 263 days |
| Day 5 | 17 Nov 2026 | 261 days |
Questions
Is an IVF due date more accurate than one from the last period?
Generally yes, because the embryo's exact age is known rather than assumed from an estimated ovulation date. Clinics still confirm dating with an early ultrasound, which is treated as the most reliable measurement.
Does this work for Day 6 transfers?
Not directly. Day 6 blastocyst transfers are less common and would use a one-day-shorter offset again (260 days); ask the clinic for the exact dating they use if the transfer was on Day 6.
Why does a Day 3 transfer add more days than a Day 5 transfer?
Because it starts two days younger. The calculator is adding whatever number of days remain to reach a 280-day pregnancy counted from the last menstrual period convention, and a Day 3 embryo has two more days of that count still to run.
Should I use this instead of my clinic's dating?
No. Use it as a general estimate. The clinic's own dating accounts for the embryo's actual grade and any cycle-specific detail, and is the figure that matters for appointments and monitoring.
For a standard last-menstrual-period due date, see the pregnancy due date calculator.