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Pregnancy calculator · Last updated October 29, 2026

IVF due date calculator

Enter your embryo transfer date and the embryo's age — 3, 5 or 6 days — to get your due date, how far along you are, and your trimester. Works for fresh and frozen transfers.

Written by Larson, D., drawing on ACOG guidance on dating IVF pregnancies.

How this is calculated

  • Due date = transfer date + 266 days − the embryo's age at transfer.
  • That works out to transfer date + 263 days for a 3-day embryo, + 261 days for a 5-day blastocyst and + 260 days for a 6-day blastocyst.
  • The same formula applies to fresh and frozen (FET) transfers, because the embryo's age is what counts.

Source: ACOG: Methods for Estimating the Due Date.

The result is an estimate from population averages, not medical advice.

At a glance

Formula used
Transfer date plus 266 days, minus the embryo's age: 263 days for a 3-day embryo, 261 for a 5-day blastocyst, 260 for a 6-day blastocyst.
Fresh or frozen
The same. Only the embryo's age on transfer day counts; time spent frozen does not.
How close it lands
As precise as dating gets, because the start is known to the day. Babies still arrive on a spread around it: roughly two-thirds within about a week either side.
Talk to a provider
Your clinic sets the official date from the transfer record and confirms the pregnancy with an early scan.

How to calculate an IVF due date

Add 266 days minus the embryo's age to your transfer date. Pregnancy lasts about 266 days from conception, and an embryo transferred on day 5 was conceived 5 days earlier, so the clock already has 5 days on it.

  • 3-day embryo: transfer date + 263 days. You are 2 weeks 3 days pregnant on transfer day.
  • 5-day blastocyst: transfer date + 261 days. You are 2 weeks 5 days pregnant on transfer day.
  • 6-day blastocyst: transfer date + 260 days. You are 2 weeks 6 days pregnant on transfer day.

A worked example

A 5-day blastocyst transferred on 10 February 2026 gives a due date of 29 October 2026 (10 February + 261 days). Had the same embryo been transferred on day 6, on 11 February, the due date would be the same day: the embryo's age and the transfer date move together.

Frozen embryo transfer (FET) due dates

A frozen transfer is dated exactly like a fresh one. What matters is how many days the embryo had developed before it was frozen, not how long it stayed frozen. A 5-day blastocyst frozen for two years still uses 261 days from the day it is transferred.

If you are not sure whether your embryo was a day 5 or day 6 blastocyst, your clinic's embryology report says. The two give due dates one day apart.

Why IVF dating is the most precise

In a natural pregnancy the due date is estimated from a last period or an ultrasound measurement. With IVF the start date is recorded to the day. ACOG's guidance is that for pregnancies conceived through assisted reproduction, the IVF-derived date should be used to set the due date, so an early scan usually confirms it rather than changing it.

Pregnancy weeks are still counted the conventional way, as if from a last period two weeks before conception. That is why you are already “2 weeks 5 days” on the day of a 5-day transfer, and why your clinic's week count runs about two weeks ahead of the embryo's real age.

Not conceived through IVF? Use the due date calculator by conception date or the due date calculator by last period.

Pregnancy week by week

Once you know how far along you are, each week's guide covers your baby's size and development, common symptoms, and what to do that week.

First trimester

Second trimester

Third trimester

All 40 weeks of pregnancy

Frequently asked questions

Add 261 days to your transfer date. A 5-day blastocyst was conceived 5 days before transfer, and pregnancy lasts about 266 days from conception, so 266 minus 5 gives 261. On the day of a 5-day transfer you are counted as 2 weeks and 5 days pregnant.

Sources and medical references

The dating rules on this page follow ACOG's guidance on estimating the due date, which covers pregnancies conceived through IVF.

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