IVF Due Date Calculator
Use this IVF due date calculator to find your due date from your embryo transfer date and embryo age, for fresh or frozen (FET) transfers.
Updated October 22, 2026
Medical Disclaimer: This calculator provides a general estimate based on established research and is for educational purposes only, not a substitute for medical advice. Individual results can vary based on health conditions, so consult a qualified healthcare professional or registered dietitian before making significant changes to your diet, exercise, or health routine. Read our full Medical Disclaimer.
How Your IVF Due Date Is Calculated
An IVF due date is the day you reach 40 weeks of pregnancy, worked out from your embryo transfer date and how many days old the embryo was. Because the lab knows the exact day the egg was fertilized, there is no need to guess when ovulation happened. The sections below show the count step by step.
What Your IVF Due Date Measures
Pregnancy is counted from the first day of a last menstrual period (LMP), about two weeks before conception, even with IVF. So the calculator works back from your transfer to an "equivalent LMP" and counts 40 weeks from there. It does not predict the day your baby will be born, and it cannot tell you whether the transfer worked. If you conceived without IVF, use the Due Date Calculator, which works from your last period, conception date, or an early ultrasound.
The Formula
Due date = transfer date + (266 minus embryo age in days)
Day 5 embryo: due date = transfer date + 261 days
Day 3 embryo: due date = transfer date + 263 days
Equivalent LMP = transfer date minus (14 + embryo age in days)
The American College of Obstetricians and Gynecologists (ACOG) says an IVF due date "should be assigned using the age of the embryo and the date of transfer," with 261 days for a day-5 embryo and 263 days for a day-3 embryo¹. The 266 is ACOG's 280-day convention, counted from the LMP, minus the 14 days before fertilization¹.
Embryo age at transfer | Days from transfer to due date | Weeks pregnant on transfer day |
Day 2 | 264 | 2 weeks 2 days |
Day 3 | 263 | 2 weeks 3 days |
Day 4 | 262 | 2 weeks 4 days |
Day 5 | 261 | 2 weeks 5 days |
Day 6 | 260 | 2 weeks 6 days |
Day 7 | 259 | 3 weeks 0 days |
How This Calculator Computes Your Result
Choose fresh or frozen, enter your transfer date, and pick the embryo's age at transfer (day 2 to day 7, default day 5). Embryo age counts from day 0, the day of egg retrieval and fertilization. Embryos are usually transferred 1 to 6 days after retrieval², and some are grown for up to 7 days before freezing³. For a fresh transfer from fresh eggs, you can enter your egg retrieval date instead, and the tool adds 266 days. The number of embryos transferred is optional and never changes the date. The math uses whole calendar days, so nothing is rounded. A future transfer date gives the due date that transfer would lead to.
What Your Result Means
Result | What it shows |
Due date | 40 weeks 0 days. The middle of a range, not a deadline. |
Gestational age today | How many weeks and days pregnant you count as, from the equivalent LMP |
Equivalent LMP | The counting start date, not a real period |
Equivalent conception date | Embryo day 0, 14 days after the equivalent LMP |
Trimester dates | First: up to 13 weeks 6 days. Second: 14 weeks 0 days to 27 weeks 6 days. Third: 28 weeks to birth. |
The trimester cutoffs follow ACOG's first-trimester definition¹ and the ICD-10 definitions used in US medical coding⁴. If your clinic or doctor gave you a different due date, use theirs. ACOG advises that a due date, once set, should only be changed in rare cases¹.
Fresh vs Frozen Embryo Transfer (FET) Due Dates
The math is the same for a fresh transfer and a frozen embryo transfer (FET). ACOG's rule uses only the embryo's age and the transfer date¹, so time in storage is not counted. Embryos frozen for more than 30 years have led to live births⁷, and a day-5 embryo frozen years ago is still entered as day 5. That is why the egg retrieval route works only for fresh transfers, since in an FET cycle the retrieval may have been years earlier. Your period dates in the FET cycle are not used either. Because the rule depends only on embryo age and transfer date, it works the same way with donor eggs, donor embryos, or a gestational carrier.
Why IVF Dating Is So Precise
Most due dates rest on an estimate. Dating from a last period assumes a 28-day cycle with ovulation on day 14, and only about half of women accurately recall their LMP¹. An early ultrasound does better, with crown-rump length dating up to 13 weeks 6 days accurate to about plus or minus 5 to 7 days¹. With IVF, the day of fertilization is known. That is why researchers test ultrasound dating against IVF pregnancies: in a study of 363 single-baby IVF pregnancies, the "true" gestational age was based on the day of egg retrieval⁵. ACOG says the IVF-derived age should be used to set the due date for these pregnancies¹.
How Close to the Due Date Babies Arrive
A precise start date does not make the birth date precise. In the same IVF study, women whose labor started on its own gave birth at an average of 279 days, or 281 days when preterm births were left out, close to the 280-day convention⁵. In a separate study of 18,708 women with spontaneous labor, only 5% gave birth on their estimated due date, and about 66% within 7 days of it⁶. Twins are dated the same way but are more likely to arrive early. The American Society for Reproductive Medicine (ASRM) notes that the risk of preterm delivery in multiple pregnancies is high, and slightly raised even for IVF singletons².
A Note on Accuracy
This is an estimate using ACOG's IVF dating rule, and it is only as accurate as the transfer date and embryo age you enter. A wrong embryo age moves the due date by the same number of days. It does not predict your pregnancy test date (your clinic sets that), whether the transfer will work, or the day you will give birth, and it does not replace your clinic's instructions about tests or medicines. Your clinic or doctor sets your official due date, and their date wins if it differs.
Frequently Asked Questions
How do you calculate an IVF due date?
Count from the transfer date: add 261 days for a day-5 embryo and 263 days for a day-3 embryo¹. In general, add 266 days minus the embryo's age in days, so a day-6 embryo is 260 days.
How many weeks pregnant am I after a 5-day transfer?
On transfer day you count as 2 weeks 5 days pregnant, then add the days since transfer. Nine days after a day-5 transfer, you are 4 weeks 0 days pregnant.
Is the due date different for a frozen embryo transfer?
No. An FET due date uses the same rule as a fresh transfer, the transfer date plus 266 minus the embryo's age in days¹. Time the embryo spent frozen is not counted.
How accurate is an IVF due date?
The start date is known almost exactly, so it is more precise than dating from a last period¹. Even so, only about 5% of babies arrive on their due date, and about two-thirds arrive within a week of it⁶.
Sources
Methods for Estimating the Due Date (Committee Opinion 700), ACOG, 2017
Assisted Reproductive Technologies, ASRM, 2018
Freezing Embryos, Johns Hopkins Medicine
Ultrasound Dating at 12-14 or 15-20 Weeks of Gestation?, Saltvedt et al., 2004
Predicting Date of Birth and Examining the Best Time to Date a Pregnancy, Khambalia et al., 2013
A Record-Breaking Baby Has Been Born From an Embryo That's Over 30 Years Old, MIT Technology Review, 2025