IVF Due Date Calculator for D3 and D5 Transfers
Enter your egg retrieval or embryo transfer date and the embryo's age to calculate an exact due date, plus today's gestational age and trimester.
Quick samples
Add your IVF date to get a precise due date.
Choose retrieval or transfer, enter the date and the embryo’s day, and your due date and today’s gestational age appear here.
This applies the standard assisted-conception formulas, which your clinic also uses, so it should match your paperwork closely. IVF dates are unusually accurate because conception timing is known, but your clinic's dating is authoritative, and a later scan can still refine it slightly. Always confirm due dates and scan windows with your fertility team and maternity provider.
The formula
Due date = retrieval + 266 days, or transfer + 266 − embryo age; implied LMP = retrieval − 14 days
- 266 days — The 38 weeks from conception to a 40-week (280-day) gestational due date.
- Embryo age — How many days old the embryo was at transfer, usually day 3 or day 5, subtracted from the count.
- Implied LMP — The notional last period, set fourteen days before retrieval, that keeps IVF dating on the gestational scale.
- Gestational age — Weeks counted from the implied LMP, the same clock used for every pregnancy.
IVF due-date rules by anchor
| Known date | Due-date formula | Implied LMP |
|---|---|---|
| Egg retrieval | Retrieval + 266 days | Retrieval − 14 days |
| Day-5 transfer | Transfer + 261 days | Transfer − 19 days |
| Day-3 transfer | Transfer + 263 days | Transfer − 17 days |
These are the standard assisted-conception formulas clinics use. A day-5 transfer subtracts five days versus a day-3 transfer subtracts three, relative to the 266-day retrieval anchor.
One quiet advantage of a pregnancy conceived through IVF is that the due date is unusually precise. Because the egg retrieval and embryo transfer happen on documented days, conception is anchored to known dates rather than estimated from a last period, so an IVF due date is calculated from real events instead of averages.
This calculator reproduces exactly what your fertility clinic does. From an egg retrieval date it adds 266 days, the 38 weeks from fertilisation to a forty-week due date. From a transfer date it first accounts for the embryo's age, since a day-5 blastocyst was conceived five days before it was transferred and a day-3 embryo three days before, then reaches the same due date.
It also translates your IVF timeline onto the gestational clock everyone else uses, by implying a last period fourteen days before retrieval. That lets you see your current weeks and days, your trimester and your due date in the same terms a midwife or OB-GYN will use, so the world of fertility treatment and the world of antenatal care line up.
Why IVF due dates are so precise
A natural-pregnancy due date is really a guess built on an assumed ovulation about a fortnight after a remembered period, and that assumption can be off by days or more if cycles are irregular. IVF removes the guessing, because the clinic records the exact day the egg was retrieved and fertilised.
Fertilisation happens in the lab on the retrieval day, so conception is known to the day rather than inferred. From that fixed point the due date is simply a set number of days forward, which is why an IVF dating is often accepted without the small corrections a scan might otherwise apply.
This tool leans on that precision. Enter the date your clinic documented and it returns the due date they would give, and a gestational age that is as reliable as the paperwork it is built on.
The one caveat is that even a precise due date predicts a birth day imperfectly, because most babies arrive within a window rather than on the date itself; precision here is about dating, not about predicting the exact day of labour.
Day-3 versus day-5 embryos
Embryos are transferred at different stages, and the stage matters for the maths. A day-5 blastocyst has spent five days growing since fertilisation before it is placed, while a day-3 cleavage-stage embryo has spent three, so the transfer dates do not correspond to the same point in the story.
To reconcile that, the calculator subtracts the embryo's age from the transfer date when working backwards, effectively returning to the retrieval and fertilisation day. Transferring a day-5 embryo means the due date is two days earlier than transferring a day-3 embryo on the same calendar day.
Choosing the day label wrongly is the commonest error here, so check your clinic notes for whether the transfer was a cleavage-stage or blastocyst embryo, and the tool will place your due date exactly where your team has it.
Fresh and frozen cycles on one clock
Whether a transfer is fresh, days after retrieval, or frozen and thawed in a later cycle, the due-date logic is the same once you know the dates, because the age of the embryo at transfer already encodes the timing. A frozen transfer months after retrieval is no harder to date than a fresh one.
The difference a frozen cycle makes is only that the implied last period is a notional clinical date, not a period you actually had, since medicated cycles may have no natural bleed at all. The calculator supplies that implied LMP so your gestational age still fits the standard forty-week scale.
This is why you may see a due date that seems to predate any period, which is expected. The implied LMP is a dating anchor, not a memory, and everything downstream counts from it consistently.
If you are ever confused by a last-period date you never experienced, this is the reason, and it is worth explaining to others, or pointing to your clinic note, rather than worrying the paperwork is wrong.
Gestational age versus your IVF timeline
Clinics sometimes speak in weeks and days since transfer or since retrieval, while maternity care speaks in gestational weeks from an LMP. The two describe the same pregnancy from different zero points, and this tool bridges them by showing both your gestational age and the underlying IVF dates.
A pregnancy three weeks after a day-5 transfer, for example, is about five weeks gestational once the two weeks before retrieval and the embryo's own age are folded in. Getting these straight prevents alarm when a scan says a different, larger number than you expected.
The percentage and trimester readouts here use the gestational convention, so they match the appointment and screening windows your maternity provider will schedule you around.
A worked example
Someone has a day-5 blastocyst transferred on a Monday and selects the transfer mode, enters the date and picks day 5. The calculator reaches back five days to the retrieval, then fourteen more to the implied LMP, and forward 266 days from retrieval to a due date.
It reports that due date alongside today's gestational age, trimester and percent through the forty weeks, so the same person can hand their maternity book around a number that agrees with the clinic's rather than one reverse-engineered from a period they never had.
Had they entered the retrieval date instead, choosing that mode and adding no embryo age, the tool would simply count 266 days forward and land on the identical due date, showing the two routes converge.
Getting the dates right
The only input that truly changes the answer is the exact retrieval or transfer date, so take it from your treatment records rather than a rough memory, and note the embryo's day as well if you are using a transfer date.
Double-check the mode you pick: a transfer date must be paired with the correct embryo age, whereas a retrieval date needs no age at all, and mixing them up is the usual source of a due date off by two days.
Finally, treat this as a precise reflection of clinic practice rather than a new authority. Your fertility team's dating governs, and any maternity scan may still refine it, so confirm your due date and screening windows with them directly.
Key terms
- Egg retrieval
- The clinic procedure when eggs are collected and fertilised, fixing the conception date.
- Blastocyst
- An embryo grown to about day 5 or 6 before transfer.
- Cleavage-stage
- A younger embryo transferred at about day 3.
- Implied LMP
- The notional last period set 14 days before retrieval, used to express IVF age as gestational weeks.
Pro tips
- Use the exact date from your treatment paperwork, not an approximation.
- Match the embryo's day (3 or 5) when dating from a transfer.
- Dating from retrieval needs no embryo age and is the simplest route.
- Your clinic's due date is authoritative; share this tool's output for context.
Common mistakes
- Entering a transfer date but leaving the wrong embryo day selected.
- Confusing weeks-since-transfer with gestational weeks.
- Expecting an implied LMP to match a real period you had.
- Rounding to a due-date month and missing a scan window.
IVF due dates — your questions
How is an IVF due date calculated?
From the egg retrieval date, the due date is retrieval plus 266 days, the 38 weeks from fertilisation to a 40-week due date. From a transfer date, you first subtract the embryo's age, so a day-5 blastocyst means transfer plus 261 days and a day-3 embryo plus 263 days. Both routes converge on the same date, and because the retrieval and transfer days are recorded, IVF dating is far more precise than a period-based estimate.
Do day-3 and day-5 transfers give different due dates?
Yes, slightly, if the transfer happens on the same calendar day. A day-5 blastocyst was fertilised five days before that transfer while a day-3 embryo was fertilised three days before, so dating from a day-5 transfer pulls the conception point back two more days and yields a due date two days earlier. Selecting the correct embryo stage in this tool is what keeps the calculation aligned with your clinic.
Is an IVF due date more accurate than a normal one?
Generally yes. A standard due date assumes ovulation about two weeks after a remembered period, which can be several days out for irregular cycles, whereas IVF anchors conception to the recorded retrieval and transfer dates. That is why clinics and maternity providers usually accept an IVF-estimated due date without the adjustments a dating scan might otherwise apply, though a later scan can still refine it slightly.
Why does the implied last period predate my cycle?
Because gestational age is counted on a scale that starts from a notional last period fourteen days before retrieval, so a pregnancy conceived through IVF shows an implied LMP that may sit before any period you actually had, or in a medicated cycle where you had none at all. It is a dating anchor, not a real bleed, and it simply places your precise IVF timeline onto the same forty-week scale used for every pregnancy.
Does frozen versus fresh change the calculation?
No, once the actual transfer or retrieval dates are known, because the embryo's age at transfer already accounts for how long it developed. A frozen transfer in a later cycle is dated the same way as a fresh one from its recorded dates. The practical difference is only that a frozen cycle's implied last period is a clinical construct rather than a period you experienced, which is normal and not an error.