IVF Due Date Calculator

How the IVF Due Date Calculator works

A standard due date estimate adds 280 days to the first day of your last period and assumes you ovulated on day 14. IVF removes that assumption. Because the egg and sperm meet in the lab on a known day, we can count forward from fertilization instead of a guessed cycle.

The baseline is fertilization date + 266 days = due date. Egg retrieval is the fertilization day, so a retrieval date gets the full 266 days. For a transfer, the embryo has already been growing for a few days, so we subtract its age:

• Day-5 (blastocyst) transfer: transfer date + 261 days
• Day-3 (cleavage) transfer: transfer date + 263 days
• Egg retrieval: retrieval date + 266 days

Frozen embryo transfer (FET)? Use the same transfer options. The due date depends on the embryo’s age and the day it was transferred, not on whether it was fresh or frozen, so a Day-5 frozen transfer is dated exactly like a Day-5 fresh one.

Gestational age is still counted from a notional last period, two weeks before fertilization. That is why you’re already “2 weeks pregnant” on retrieval day — it’s a convention every pregnancy app and clinic shares, not a quirk of this tool.

Why IVF dating is more precise

With a natural conception, the due date hinges on two unknowns: the exact day you ovulated and how long your cycle runs. Both can shift the estimate by several days, or more if your cycles are long or irregular. IVF replaces those unknowns with a calendar entry from the lab, so the starting point is exact.

Precise math still isn’t the final word. Babies arrive across a normal range of roughly 37 to 42 weeks, and your clinic’s first ultrasound — usually around 6 to 8 weeks — checks the heartbeat and confirms the pregnancy. For IVF, doctors set the due date from your transfer date and embryo age, the same math used here. If your clinic gives you a different date, go with theirs. Treat this tool as a friendly planning estimate while you wait for that appointment.

When to check in with your clinic

This calculator is for planning and reassurance, not monitoring. Reach out to your fertility clinic or healthcare provider — don’t wait for a scheduled appointment — if you have:

• Heavy bleeding, severe cramping, or sharp one-sided pain
• Feeling very dizzy or fainting, sudden sharp tummy pain, or shoulder-tip pain — these can be signs of internal bleeding, so get emergency help now (call 999 in the UK or 911 in the US)
• A positive then suddenly negative pregnancy test
• Any symptom that worries you, however small it seems

Your IVF team scheduled your beta-hCG blood tests and early scans for a reason — those, not a due-date estimate, are how a pregnancy is confirmed and followed.