IVF Due Date Calculator

IVF dating is more exact than dating from a last period, because the age of the embryo on the day of transfer is known rather than estimated. There is no cycle-length guesswork involved.

Select what your clinic date refers to, whether that is a day 3 or day 5 transfer, a frozen transfer, egg retrieval or an IUI, and the calculator works out the due date and matching gestational age.

These calculators provide estimates for informational purposes only. They are not intended to diagnose, treat, prevent, or replace professional medical advice. Pregnancy and menstrual cycles can vary, so results may not be exact.

How this calculator works

What you need to enter:

Your embryo transfer date, egg retrieval date or IUI date
The embryo's age on the day of transfer, which your clinic will have told you

The formula

A pregnancy runs about 266 days from conception. In IVF, day 0 of embryo development is the day of fertilisation, so the calculation is the transfer date plus 266 days minus the embryo's age at transfer.

A day 5 blastocyst has already used five of those days by the time it is transferred, so 261 days remain. A day 3 embryo has used three, leaving 263. Egg retrieval and IUI are day 0, so they carry the full 266.

Day 3 transfer: transfer date + 263 days
Day 5 transfer: transfer date + 261 days
Day 6 transfer: transfer date + 260 days
Day 7 transfer: transfer date + 259 days
Egg retrieval or IUI: date + 266 days

Fresh and frozen transfers

The formula is the same for a fresh transfer and a frozen embryo transfer. What matters is the age the embryo had reached when it was frozen, because development pauses during freezing and resumes on thawing.

So a blastocyst frozen on day 5 and transferred months later is still a day 5 embryo for dating purposes. Use the age your clinic recorded, not the time it spent frozen.

Why the gestational age looks odd at first

Gestational age is counted from a notional last menstrual period, two weeks before conception. On the day of a day 5 transfer you are already 2 weeks and 5 days pregnant by that convention, even though the embryo is five days old.

This is not an error. It keeps IVF pregnancies on the same 40-week scale as everyone else, so scans, tests and appointment timings line up in the usual way.

A worked example

A day 5 blastocyst transferred on 1 March 2027.

The embryo was 5 days old at transfer, so day 0 of development was 24 February 2027.
Add 266 days to 24 February 2027.
The estimated due date is 17 November 2027, which is 261 days after the transfer.
On transfer day the gestational age was 2 weeks and 5 days.

A day 3 embryo transferred on the same date would be due two days later, on 19 November 2027.

What this calculator can't tell you

The estimate is precise about dating but says nothing about how a pregnancy will progress.
Use the embryo age your clinic recorded. Guessing between day 5 and day 6 shifts the date by a day.
Your clinic's own dating takes precedence. Clinics occasionally use slightly different conventions.
As with any pregnancy, birth commonly happens in the weeks either side of the estimated date.

What to do next

Check how far along you are today with the pregnancy week calculator.
See the full timeline and milestone dates in the pregnancy calculator.

Common questions

How is an IVF due date calculated?

By adding 266 days to the embryo's day 0 of development. In practice that means adding 261 days to a day 5 transfer date, 263 to a day 3 transfer, or 266 to an egg retrieval or IUI date. Because the embryo's age is known exactly, no cycle-length assumption is needed.

Is an IVF due date more accurate than a standard one?

For dating purposes, yes. Standard dating assumes ovulation happened around day 14 of a 28-day cycle, which is often wrong by a few days. IVF dating starts from a known fertilisation date, so the estimate is not affected by cycle variation. It still describes a likely range for birth, not a fixed day.

Does a frozen embryo transfer use a different formula?

No. Use the embryo's age at the time it was frozen. A day 5 blastocyst is dated as a day 5 embryo regardless of how long it spent frozen, because development is paused rather than continuing.

Why does the calculator say I am already pregnant on transfer day?

Gestational age is counted from a notional last period about two weeks before conception, so everyone starts the count at roughly two weeks. On the day of a day 5 transfer that works out to 2 weeks and 5 days. It keeps IVF pregnancies on the same 40-week scale as any other.

What if I do not know the embryo's age at transfer?

Your clinic will have it in your treatment records, and it is worth checking rather than guessing. Day 5 blastocyst transfers are the most common, but the difference between day 3 and day 5 moves the due date by two days.