IVF due date calculator: how day 3, day 5 and day 6 transfers give your due date

After an embryo transfer, the first thing most couples want is a date. The clinic may hand you one, but it helps to know how it was worked out, and why it does not match the period based calculators you find online. An IVF due date is the easiest due date of all to calculate, because the age of the embryo is known to the day.

This guide shows the rule doctors use, the numbers for day 3, day 5 and day 6 embryos, and what changes for a frozen transfer. Every date below was worked out by the code behind our free due date calculator, which has an IVF transfer option built in.

The short answer

Take the date of the embryo transfer and add a fixed number of days that depends on how old the embryo was on that day.

The day 3 and day 5 numbers come straight from the American College of Obstetricians and Gynecologists (ACOG). Its Committee Opinion 700 says that for a pregnancy from IVF, the due date should be assigned using the age of the embryo and the date of transfer, and gives the two examples: 261 days from the transfer for a day 5 embryo and 263 days for a day 3 embryo. Day 6 follows the same logic, one day less again.

Why 261 and 263?

A pregnancy lasts about 266 days from fertilisation to the due date. Doctors add two extra weeks at the start, because pregnancy is traditionally counted from the first day of the last period, and ACOG puts the due date 280 days after that. 280 minus 266 is the 14 days before ovulation in a textbook 28 day cycle.

An embryo's day number counts days since fertilisation, which in IVF happens in the lab on the day the eggs are collected. A day 5 embryo has already used up 5 of the 266 days, so 261 are left. A day 3 embryo has used 3, so 263 are left. That is the whole calculation.

It also explains the weeks on your scan report. On the day of a day 5 transfer you are already counted as 2 weeks 5 days pregnant, even though the embryo went in that morning. The calculator shows this as week 0, the date your pregnancy count starts. For a day 5 transfer on 1 October 2026, week 0 is 12 September 2026.

A worked example

Say a day 5 blastocyst was transferred on 1 October 2026. We ran this on the live calculator on 28 Oct 2026.

The due date is Saturday, 19 June 2027. On 28 October 2026 that pregnancy is 6 weeks 4 days, in the first trimester, with 234 days to go. The likely conception date shown, around 26 September 2026, is simply the transfer date minus the embryo's 5 days, so for IVF it is the day of egg collection.

Day 3 or day 5 from the same egg collection: same due date

People often ask whether a day 5 transfer makes the baby due earlier. For the same transfer date, yes, by two days, because the embryo is two days older. But if the eggs were collected on the same day, it makes no difference at all. Eggs collected on 26 September 2026 give a due date of 19 June 2027 whether the embryo goes in on day 3 (29 September), day 5 (1 October) or day 6 (2 October). The calculator agrees on all three.

So if you know your egg collection date but not the embryo day, choose Conception in the calculator and pick the collection date. It adds 266 days and lands on the same due date.

Frozen embryo transfer (FET)

ACOG's wording does not treat fresh and frozen transfers differently. It only asks for two things: the age of the embryo and the date of transfer. The months or years an embryo spent frozen are not part of the rule. For a frozen day 5 blastocyst thawed and transferred on 1 October 2026, the due date is 19 June 2027, the same as a fresh one.

Check the embryo age on your clinic's transfer note. Most frozen transfers today are blastocysts, but some clinics freeze on day 3 or day 6, and that changes the answer by a day or two.

What about IUI or a scan that disagrees?

IUI has no embryo transfer, so the IVF rule does not apply. Use Last period, or Conception if your doctor gives you an ovulation or insemination date, and expect the early scan to confirm it.

After IVF, ACOG says the date from the treatment should be used to set the due date. A first trimester scan measuring the baby's crown to rump length is accurate to about 5 to 7 days, so a scan that reads a couple of days ahead or behind is normal and is not a reason to change the date. If your doctor does set a different date, choose Due date in the calculator and pick it, so the weeks match your reports.

Quick lookup: due dates by transfer date

How to use the calculator

1. Open the due date calculator and tap IVF transfer under Work it out from.
2. Pick the Embryo transfer date, then tap Day 3, Day 5 or Day 6 under Embryo age.
3. Press Calculate due date. The due date comes first, then how many weeks pregnant you are today, the trimester and the days left.
4. To see the weeks on another day, such as a scan or a family event, open More options and change Show the weeks on. The pregnancy week calculator does the same with weeks as the headline.
5. Press Download calendar (.ics) to put all the dates in Google Calendar, Outlook or your phone, or Copy summary to share them.

Are the dates sent anywhere?

No. The dates are worked out in your browser tab and are not sent to TaskNinja or saved. While taking the screenshot we watched the network: after the page loaded, the only requests were routine pings from Google's ad script, and none of them contained the transfer date or the due date.

A due date is an estimate. Full term alone spans two weeks, so treat the date as the middle of a window. Your fertility clinic and obstetrician have the final word.

FAQ

How many days do you add for a day 5 transfer?

Add 261 days to the transfer date. A day 5 transfer on 1 October 2026 is due on 19 June 2027. ACOG gives this example in Committee Opinion 700.

How do you calculate a due date after a day 3 transfer?

Add 263 days to the transfer date. On the day of a day 3 transfer you are counted as 2 weeks 3 days pregnant.

Is the due date different for a frozen embryo transfer?

No. The rule uses the embryo's age and the transfer date, whether the embryo was fresh or frozen. Time spent frozen is not counted.

How many weeks pregnant am I after a day 5 transfer?

2 weeks 5 days on the transfer day. Add the days since then. Four weeks after a day 5 transfer you are 6 weeks 5 days.

My scan says a different due date. Which one is right?

For an IVF pregnancy, ACOG says the date from the treatment should be used. Early scans are accurate to about 5 to 7 days, so small gaps are expected. Follow the date your doctor writes in your records.

Sources

• ACOG Committee Opinion 700, Methods for Estimating the Due Date (2017, reaffirmed 2025)
• Full text of Committee Opinion 700 in Obstetrics & Gynecology (IVF 261 and 263 days, 280 days from the last period, crown to rump length accuracy)
• ACOG Committee Opinion 579, Definition of Term Pregnancy (early, full, late and postterm)
• WHO news release, 7 November 2016: eight antenatal contacts and one ultrasound before 24 weeks

Sources checked 28 Oct 2026. Every date in the tables comes from our calculator's code on that date. General information, not medical advice.

Written by the TaskNinja team with help from an AI writing tool, then checked against the ACOG and WHO sources above and the tool itself.