FET due date calculator

Estimate a due date after frozen embryo transfer from the FET date and embryo day age. Freeze storage time does not add pregnancy weeks. Estimate only — not medical advice.

Embryo age at transfer

FET date

Enter a transfer date to see an estimate.

What this page does

Frozen embryo transfer dating is still day-age math — not "freeze months plus pregnancy weeks." A Day 5 blastocyst transferred after thaw uses the same +261 style offset as a fresh Day 5 transfer. The tank does not get its own second pregnancy clock, no matter how long the embryo waited.

Enter your FET date and embryo age to get an estimated due date you can compare with the clinic calendar. Medicated lining checks, thaw calls, and progesterone clocks change how the cycle feels; they do not invent a separate FET-only due-date universe.

If your clinic already stuck an EDD in the portal, treat this as a sanity check. If a dating ultrasound later updates that number, follow the clinic. This page exists because consumer apps keep asking for a last period after FET and then drifting a week when you invent one.

When to use

You are scheduling life around a FET and want the EDD without translating through a fake LMP. Your paperwork says "FET Day 5" and a consumer app keeps asking for the first day of your last period.

Also useful when comparing a medicated FET calendar to a natural-cycle FET — the meds and monitoring differ, the day-age add-on idea stays the same. Partners often hear "frozen" and assume the math is exotic; showing +261 from FET day usually ends that thread.

When not to

If you had a fresh transfer, the main IVF due date page is the better hub. If a dating ultrasound already reset your EDD, follow the clinic.

Do not add storage time in the freezer as if those months were gestational age. Do not date from the original freeze year. Do not use this to rewrite beta instructions your clinic already printed.

Assumptions

FET uses the thawed embryo's day age: Day 3 → +263, Day 5 → +261, Day 6 → +260 from the FET date.

We do not adjust for assisted hatching notes, endometrium lining thickness, protocol brand names, or how many years the embryo spent frozen. Those matter clinically; they are not separate calendar add-ons in this tool. Thaw survival is assumed — you are dating a transfer that happened.

Examples

FET Day 5 · February 2, 2026 → EDD October 21, 2026. +261 from FET date.

FET Day 3 · February 2, 2026 → EDD October 23, 2026. +263 — two days later than Day 5 on the same FET date.

FET Day 6 · July 12, 2026 → EDD March 29, 2027. +260 for Day 6.

Gotchas

Freeze date ≠ FET date. Dating starts when the embryo is transferred, not when it entered storage.

"Natural FET" vs "medicated FET" changes monitoring and meds, not the basic day-age offset family.

If you transferred two embryos of different ages, ask which dating rule your clinic applies.

Storage duration myths ("it was frozen three years so add three years") are wrong for due dates.

PGT-tested embryos are still dated by day age at transfer, not by biopsy day.

A portal EDD after ultrasound can differ from pure FET math — follow clinic policy when they diverge.

How this is calculated

Treat FET like any other transfer for dating: the date the embryo went in, plus how old it already was.

The freeze date belongs in storage records, not in the due-date add-on. If your paperwork is vague about Day 5 vs Day 6, ask before you lock a leave form to the wrong day.

Confirm embryo age on the FET paperwork (often Day 5 blastocyst).
Enter the FET date, not the original freeze date and not the retrieval year.
Read the estimated due date from the day-age offset.
If your clinic quotes an LMP-equivalent for hospital forms, cross-check with the LMP-equivalent tool.
After a dating scan, prefer the clinic's updated EDD over napkin math.
Ignore "add the years it was frozen" advice from well-meaning relatives — that is not gestational age.

EDD ≈ FET date + (266 − embryo age)
Common default: Day 5 FET → +261

Related calculators

Fresh-transfer wording sits on the IVF hub and the calculate-from-IVF page. Day 5 blastocyst has its own landing for that exact search, whether fresh or frozen.

If the real problem is a hospital form that only understands LMP, build an LMP-equivalent after you have the EDD. If you only have an EDD and no FET date handy, reverse dating is the better entry point.

FAQ

How do you calculate a due date after FET?: From the FET date plus the embryo's day age offset — commonly +261 for a Day 5 blastocyst. Freezer time is not added as pregnancy length. Day 3 uses +263; Day 6 uses +260.
Is FET dating different from fresh IVF?: The day-age idea is the same. What changes is your protocol and monitoring, not a separate "frozen pregnancy calendar." A Day 5 FET and a fresh Day 5 transfer share the same style of add-on from their respective transfer days.
My app asks for LMP after FET — what do I enter?: Not a fictional period from your memory. Use an IVF LMP-equivalent built from your EDD, or skip apps that cannot handle transfer dating. Inventing menses is how people get a week off.
Does a Day 6 FET change the math?: Yes — Day 6 uses +260 from FET date, because one more embryo day has already passed before transfer. Calling every blastocyst "Day 5" for convenience will nudge the EDD.
Can a scan change my FET due date?: Yes. Early ultrasound dating can update the official EDD; clinics generally follow their scan policy afterward. Use this page as a check, not a veto.
Does how long the embryo was frozen matter for the due date?: Not in this dating model. Storage duration is irrelevant to the day-age add-on. A 2019 freeze and a 2026 freeze use the same math for the same day age at FET.
Natural-cycle FET vs programmed FET — which changes dating?: Protocols differ for meds and monitoring. The basic day-age EDD math usually does not. Ask your clinic if they apply a special adjustment — do not assume the internet invented one.
Is this medical advice?: No. Estimate only — confirm with your clinic.