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IVF Due Date Calculator

HealthPregnancy and Fertility

The day the embryo was placed in the uterus, fresh or frozen cycle.

Embryo age at transfer
Estimated due date (YYYY-MM-DD) —
Due date written out
—
Equivalent last menstrual period
—
Equivalent fertilisation date
—
Pregnancy age on transfer day
—
Second trimester begins
—
Third trimester begins
—
Days from transfer to due date
—

An IVF due date is the transfer date plus 266 days minus the embryo's age. A day-5 blastocyst transferred on 10 January 2026 gives 261 days and a due date of 28 September 2026; a day-3 embryo on the same day gives 263 days and 30 September 2026. Because the fertilisation date is known exactly, IVF dating is the most precise there is.

About this tool

After an embryo transfer, clinics date the pregnancy from the transfer itself rather than from a period, since the age of the embryo is known to the day. This calculator takes the transfer date and whether the embryo was transferred on day 3, 5 or 6, and returns the estimated due date along with the equivalent last menstrual period that scan reports and pregnancy apps expect, the equivalent fertilisation date, how far along the pregnancy counts on transfer day, and the dates each trimester begins. Fresh and frozen cycles use the same arithmetic, as do donor-egg cycles. One limit: the result is a 40-week estimate for a single pregnancy; twins and other multiples are usually delivered earlier, and your clinic's dating scan remains the reference.

How to use it

  1. Enter the transfer date

    Pick the calendar day the embryo was placed, from your clinic's transfer notes.

  2. Choose the embryo age

    Select day 3 for a cleavage-stage embryo, day 5 or day 6 for a blastocyst.

  3. Read the due date and milestones

    The due date appears with the equivalent LMP, fertilisation date, and trimester start dates, plus the arithmetic used.

Examples

Day-5 blastocyst transferred 10 January 2026

Embryo transfer date
2026-01-10
Embryo age at transfer
Day 5

Result Estimated due date (YYYY-MM-DD): 2026-09-28
Due date written out: September 28, 2026
Equivalent last menstrual period: 2025-12-22
Equivalent fertilisation date: 2026-01-05
Pregnancy age on transfer day: 2 weeks 5 days
Second trimester begins: 2026-03-30
Third trimester begins: 2026-07-06
Days from transfer to due date: 261

  1. Embryo age at transfer = 5 days
  2. Days from transfer to due date = 266 − 5 = 261
  3. Due date = 2026-01-10 + 261 days = 2026-09-28
  4. Equivalent LMP = 2026-01-10 − (14 + 5) days = 2025-12-22
  5. Gestational age on transfer day = 2 weeks 5 days

ACOG adds 261 days to a day-5 transfer date, which lands on 28 September 2026. The pregnancy is counted as 2 weeks 5 days on transfer day.

Day-3 embryo transferred 10 January 2026

Embryo transfer date
2026-01-10
Embryo age at transfer
Day 3

Result Estimated due date (YYYY-MM-DD): 2026-09-30
Due date written out: September 30, 2026
Equivalent last menstrual period: 2025-12-24
Equivalent fertilisation date: 2026-01-07
Pregnancy age on transfer day: 2 weeks 3 days
Second trimester begins: 2026-04-01
Third trimester begins: 2026-07-08
Days from transfer to due date: 263

  1. Embryo age at transfer = 3 days
  2. Days from transfer to due date = 266 − 3 = 263
  3. Due date = 2026-01-10 + 263 days = 2026-09-30
  4. Equivalent LMP = 2026-01-10 − (14 + 3) days = 2025-12-24
  5. Gestational age on transfer day = 2 weeks 3 days

A day-3 embryo is two days younger than a blastocyst, so 263 days are added and the date moves to 30 September 2026.

Day-6 frozen transfer on 15 June 2027

Embryo transfer date
2027-06-15
Embryo age at transfer
Day 6

Result Estimated due date (YYYY-MM-DD): 2028-03-01
Due date written out: March 1, 2028
Equivalent last menstrual period: 2027-05-26
Equivalent fertilisation date: 2027-06-09
Pregnancy age on transfer day: 2 weeks 6 days
Second trimester begins: 2027-09-01
Third trimester begins: 2027-12-08
Days from transfer to due date: 260

  1. Embryo age at transfer = 6 days
  2. Days from transfer to due date = 266 − 6 = 260
  3. Due date = 2027-06-15 + 260 days = 2028-03-01
  4. Equivalent LMP = 2027-06-15 − (14 + 6) days = 2027-05-26
  5. Gestational age on transfer day = 2 weeks 6 days

260 days after 15 June 2027 crosses 29 February 2028 and lands on 1 March 2028.

How it is calculated

Due date = transfer date + (266 − embryo age); equivalent LMP = transfer date − (14 + embryo age)

266
Days from fertilisation to a 40-week due date (280 days minus the 14 days before ovulation)
embryo age
Days since fertilisation at transfer: 3, 5 or 6
14
Days conventionally counted from LMP to ovulation

Obstetric dating counts 280 days from the first day of the last period, assuming ovulation on day 14. In IVF the fertilisation day is the egg retrieval day, so the pregnancy is 266 days from due date at fertilisation. Subtracting the embryo's age gives the days left on transfer day: 263 for day 3, 261 for day 5 and 260 for day 6, matching ACOG Committee Opinion 700. Trimesters are taken to begin at 14 weeks 0 days and 28 weeks 0 days from the equivalent LMP.

Sources

When not to use it

  • Do not use it for a natural or IUI conception, where the date of fertilisation is not known.
  • It does not adjust for twins or triplets, which are usually delivered before 40 weeks.
  • If your clinic has issued a dating-scan due date, that date takes precedence for care decisions.

Common mistakes

  • Entering the egg retrieval date instead of the transfer date shifts the result by three to six days.
  • Choosing day 5 for a day-6 blastocyst moves the due date one day later than the clinic's.
  • Counting a frozen embryo's age from when it was thawed rather than from fertilisation.

Frequently asked questions

Does a frozen embryo transfer change the due date maths?

No. A frozen embryo stops ageing while stored, so its developmental age at transfer is the age at which it was frozen, usually day 5 or day 6. Add 261 days for a day-5 blastocyst or 260 for a day-6 one, the same as in a fresh cycle.

Why is my IVF pregnancy already 2 weeks 5 days on transfer day?

Pregnancy is counted from an assumed last period two weeks before ovulation. A day-5 embryo is five days past fertilisation, so on transfer day the pregnancy is 14 + 5 = 19 days along, written as 2 weeks 5 days. This keeps IVF pregnancies on the same scale as natural ones.

What equivalent LMP should I give a sonographer or app?

Use the equivalent LMP stat: the transfer date minus 14 days and minus the embryo age. For a day-5 transfer on 10 January 2026 that is 22 December 2025. Entering it into a standard pregnancy app reproduces the same due date.

Is an IVF due date more reliable than one from a period?

Yes, in terms of dating. ACOG states that pregnancies from assisted reproductive technology should be dated from the embryo age and transfer date, because the moment of fertilisation is known rather than estimated. The date of birth itself still varies across the full-term window of 39 to 41 weeks.

How does a donor egg cycle affect the due date?

It does not. The calculation depends only on the embryo's age and the transfer date, not on whose egg was used or the recipient's cycle. A day-5 donor blastocyst transferred on any date is due 261 days later.

What if my embryo was transferred on day 2 or day 4?

This calculator offers day 3, 5 and 6, which cover almost all transfers. For other ages the same rule applies: add 266 minus the embryo's age in days, so a day-2 transfer adds 264 days and a day-4 transfer adds 262.

Cite this tool

Using this tool in an assignment, article or report? Copy a citation, or a link for your website.

APA

Tools Directory Editorial Team. (2026, October 19). IVF Due Date Calculator. Tools Directory. Retrieved October 27, 2026, from https://tools.milunir.com/health/pregnancy-and-fertility/ivf-due-date-calculator/

MLA

Tools Directory Editorial Team. “IVF Due Date Calculator.” Tools Directory, 19 Oct. 2026, https://tools.milunir.com/health/pregnancy-and-fertility/ivf-due-date-calculator/. Accessed 27 Oct. 2026.

Chicago

Tools Directory Editorial Team. “IVF Due Date Calculator.” Tools Directory. Last modified October 19, 2026. Accessed October 27, 2026. https://tools.milunir.com/health/pregnancy-and-fertility/ivf-due-date-calculator/.

Link<a href="https://tools.milunir.com/health/pregnancy-and-fertility/ivf-due-date-calculator/">IVF Due Date Calculator – Tools Directory</a>