1
Pregnancy & Baby
IVF Due Date Calculator — Day 3 & Day 5 Embryo Transfer
Why an IVF pregnancy is dated from the transfer, not a last period — and how Day 3 vs Day 5 changes the math
An IVF pregnancy is dated differently from a spontaneous one, and that single fact is what this page exists to handle. Because your embryo was fertilized in a lab and transferred on a known calendar day, there's no guessing about ovulation or a last period — the timing of your transfer is the anchor. That makes transfer-based due dates among the tightest estimates in obstetrics. The one thing you can't skip is how many days old the embryo was when it was transferred, because the answer changes the arithmetic. If you've already used our standard Due Date Calculator and gotten a date that felt wrong, this is almost always why: a last-period wheel can't read a transfer date correctly.
Here's the foundation specific to embryo transfers. Obstetrics counts a full term as 266 days from fertilization (the same finish line as 280 days, or 40 weeks, from a last period — the clinic simply tacks on the conventional 14 pre-ovulation days). In IVF the embryo is already several days into development when it's placed back, so we subtract that head start:
Due date = transfer date + 266 − (embryo age in days)
That reduces to the two transfer rules this page owns:
• Day 5 blastocyst transfer → due date = transfer date + 261 days. (266 − 5) • Day 3 embryo transfer → due date = transfer date + 263 days. (266 − 3)
Worked example. A Day 5 blastocyst transferred on March 1, 2026 plus 261 days lands on November 17, 2026 — your estimated due date. The same date as a Day 3 transfer adds 263 days and lands on November 19, 2026. The two extra days a Day 5 spent maturing in the lab are exactly why its due date sits two days earlier than the Day 3 version. The tool also returns your current gestational age in weeks and days on the 40-week clock — so a just-completed Day 5 transfer already reads as roughly 2 weeks 5 days — along with the matching pregnancy stage for appointment and travel planning.
The number-one error here is treating the transfer day as conception day and ignoring embryo age — adding a flat 266 days no matter what. That pushes a Day 5 estimate 5 days too far and a Day 3 estimate 3 days too far. The second trap, unique to frozen cycles, is dating from the egg-retrieval day instead of the transfer day; only the day the embryo entered the uterus counts.
Treat this as a planning estimate, not a clinical due date or medical advice. In an IVF pregnancy your fertility clinic owns the official due date, and the early viability scan they schedule — typically around 6 to 8 weeks — is what they'll use to confirm or fine-tune it. Treat any number here as a planning figure until that scan.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Due date = transfer date + 266 days − (embryo age in days) • Day 5 blastocyst: due date = transfer date + 261 days • Day 3 embryo: due date = transfer date + 263 days • Gestational age on transfer day = 14 days + embryo age (LMP convention) • Current gestational age = (today − (due date − 280 days)), shown as weeks + days • Trimester: 1st = up to 13w 6d · 2nd = 14w 0d–27w 6d · 3rd = 28w 0d onward
📰 Formula
• Due date = transfer date + 266 days − (embryo age in days) • Day 5 blastocyst: due date = transfer date + 261 days • Day 3 embryo: due date = transfer date + 263 days • Gestational age on transfer day = 14 days + embryo age (LMP convention) • Current gestational age = (today − (due date − 280 days)), shown as weeks + days • Trimester: 1st = up to 13w 6d · 2nd = 14w 0d–27w 6d · 3rd = 28w 0d onward
🧪 Worked examples
2
Example 2
3
Example 3
4
Example 4
⚠️ Common mistakes
- Treating the transfer date as conception day and adding a flat 266 days (ignores embryo age).
- Using the egg-retrieval date instead of the actual embryo transfer date.
- Mixing up Day 3 and Day 5 — they differ by 2 days in the due date.
- Dating from your last period the standard way; IVF is dated from the transfer.
💡 Tips
- Always date from the transfer day, not the egg retrieval, especially in frozen (FET) cycles.
- A Day 5 blastocyst due date is exactly 2 days earlier than the Day 3 version of the same transfer date.
- Because transfer timing is exact, the early viability scan usually confirms this date rather than changing it — but the clinic's number is always the official one.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/ivf-due-date-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How is an IVF due date calculated?
Add 266 days to your transfer date, then subtract the embryo's age. In practice that's transfer date + 261 days for a Day 5 blastocyst, or transfer date + 263 days for a Day 3 embryo.
What's the difference between a Day 3 and a Day 5 due date?
A Day 5 blastocyst has grown two extra days in the lab, so you subtract two more days. The Day 5 due date is exactly 2 days earlier than the Day 3 due date for the same transfer date.
Is an IVF due date more accurate than a regular one?
Usually yes. A spontaneous pregnancy is dated with the last-period method behind our standard Due Date Calculator, which leans on recalling a last period and assuming a day-14 ovulation. IVF removes both unknowns: the lab knows the fertilization day and the transfer day exactly, so the estimate starts on firmer ground. The viability scan still serves as the final check.
How many weeks pregnant am I right after a Day 5 transfer?
By the standard 40-week (LMP) convention you're about 2 weeks and 5 days along on transfer day — pregnancy is counted from roughly 14 days before conception, plus the 5 days the blastocyst already grew.
Do I count from the egg retrieval or the transfer date?
Count from the transfer date — the day the embryo was placed in the uterus. This matters most in frozen embryo transfer (FET) cycles, where retrieval may have been months earlier.
How do I find my due date for a frozen embryo transfer (FET)?
Use the same rules: FET transfer date + 261 days for a Day 5 blastocyst, or + 263 days for a Day 3 embryo. The freezing time in between doesn't change the math.
When do the trimesters start in an IVF pregnancy?
An embryo transfer doesn't change the trimester boundaries — they're keyed to gestational age, which this tool already reports on the 40-week clock. Because a Day 5 transfer puts you near 2w 5d on transfer day, you reach the start of the second trimester (14w 0d) sooner on the calendar than you might expect, then the third trimester at 28w 0d. The clock, not the conception method, sets the milestones.
Can my IVF due date change?
Less often than with a last-period date. Because the transfer timing is already exact, the viability scan usually confirms the transfer-based due date rather than moving it; large revisions are uncommon in IVF pregnancies. If the clinic does adjust it by a day or two, their number is the one that stands.
Is this calculator a substitute for my doctor?
No. It's an informational estimate to help you plan. Your fertility clinic and obstetrician set your official due date and monitor your pregnancy — always confirm with them.