IVF Due Date Calculator — Transfer Date or LMP
This IVF due date calculator finds your due date from a day 3 or day 5 embryo transfer, egg retrieval, last menstrual period or conception date. See gestational age today, trimester and key milestones — calculated privately in your browser.
IVF dates follow ACOG guidance: transfer date + 261 days (day 5) or + 263 days (day 3); egg retrieval + 266 days.
Key Milestones
An IVF due date calculator estimates when a baby conceived through in vitro fertilization is due, using the embryo transfer date and the embryo's age instead of a last period. Because the embryo's age is known exactly, the due date is the transfer date plus 266 days minus the embryo's age: 261 days for a day-5 blastocyst, 263 for a day-3 embryo.
How the IVF Due Date Calculator Works
A natural pregnancy is counted from the first day of the last menstrual period (LMP), about 14 days before conception, and lasts 280 days. In IVF, fertilization happens in the lab on the day of egg retrieval, so that day is treated like conception: retrieval date + 266 days. An embryo transferred on day 5 is already 5 days old, so you add 5 fewer days (261); a day-3 embryo gets 263. This is the method in ACOG Committee Opinion 700, Methods for Estimating the Due Date, which says IVF pregnancies should be dated from the embryo's age and the transfer date. The calculator also shows the equivalent LMP date (transfer date minus 14 days minus the embryo's age), which is what your obstetrician uses to count weeks.
| Start date (Oct 1, 2026) | Days added | Equivalent LMP | Estimated due date |
|---|---|---|---|
| Day 5 blastocyst transfer | +261 | Sep 12, 2026 | Jun 19, 2027 |
| Day 3 embryo transfer | +263 | Sep 14, 2026 | Jun 21, 2027 |
| Egg retrieval / fertilization | +266 | Sep 17, 2026 | Jun 24, 2027 |
Frozen embryo transfers use the same rule — what matters is the embryo's age on the day it is transferred, not when it was frozen. On October 6, 2026, the day-5 example above would be 3 weeks 3 days pregnant.
LMP vs Ultrasound vs IVF Due Date: Which Is Most Accurate?
| Dating method | Starting point | Formula | Main source of error |
|---|---|---|---|
| Last menstrual period | First day of last period | LMP + 280 days | Assumes ovulation on day 14; irregular or long cycles shift it |
| First-trimester ultrasound | Crown-rump length scan | Measured size → gestational age | Accurate to about ±5–7 days up to 13 weeks 6 days |
| IVF / ART dating | Embryo transfer or egg retrieval | Transfer + 266 − embryo age | Embryo age is known, so ACOG uses ART dating for these pregnancies |
For a spontaneous pregnancy, an early ultrasound often refines an LMP-based date. For an IVF pregnancy, ACOG Committee Opinion 700 says the ART-derived gestational age should be used to assign the due date.
How the Due Date Calculator Works for LMP and Conception
This calculator uses Naegele's rule, the standard medical method for estimating pregnancy due dates. From the Last Menstrual Period (LMP), the estimated due date is calculated by adding 280 days (40 weeks). If you provide a conception date instead, the calculator adds 266 days (38 weeks), since conception typically occurs about 14 days after the LMP.
Naegele's Rule
Due Date = LMP + 280 days (40 weeks)
Due Date = Conception Date + 266 days (38 weeks)
Most pregnancies last between 37 and 42 weeks. The estimated due date represents the midpoint of this range. Only about 4–5% of babies are born on their exact due date.
Understanding Trimesters
Pregnancy is divided into three trimesters. The first trimester spans weeks 1-12 and involves rapid cell division and organ formation. The second trimester (weeks 13-26) is often considered the most comfortable period, with the baby growing significantly. The third trimester (weeks 27-40) prepares both mother and baby for delivery, with the baby gaining weight and the lungs maturing.
Important Disclaimer
This calculator provides an estimate only and is not a substitute for professional medical advice. For IVF pregnancies, use the due date your fertility clinic assigns; for other pregnancies, an early ultrasound by your healthcare provider can confirm or adjust the date. Always consult your doctor or midwife for personalized prenatal care.
Tips for Getting Accurate Results
Pick the method that matches what you actually know. After IVF, choose the transfer type from your clinic paperwork — a day-5 blastocyst and a day-3 embryo transferred on the same day give due dates two days apart. If you only know your last period and your cycles are irregular, treat the result as a rough guide until an early scan. Save or screenshot your results to compare with your clinic's dating.
Sources: ACOG Committee Opinion No. 700 (2017), Methods for Estimating the Due Date. Last updated: October 2026.
Frequently Asked Questions
Is my health data sent to any server?
Absolutely not. This calculator runs entirely in your browser using JavaScript. Your dates, results, and health information are never transmitted, stored, or shared with any server or third party. Your privacy is our top priority, especially with sensitive health data.
How accurate is the due date estimate?
Naegele's rule is the standard medical method and provides a reliable estimate. However, only about 4-5% of babies are born on their exact due date. Most arrive within a two-week window around the estimated date. Ultrasound dating by your healthcare provider offers more precise results.
What is the difference between LMP and conception date?
LMP (Last Menstrual Period) is the first day of your last period. Conception typically occurs about 14 days after the LMP during ovulation. If you know your conception date, select that option for a slightly more precise calculation. Both methods use established medical formulas.
Can I use this calculator on my phone?
Yes. The calculator is fully responsive and works on smartphones, tablets, and desktop computers. Since it runs entirely in your browser, it even works offline once the page has loaded.
Is this IVF due date calculator free to use?
Yes, this IVF and pregnancy due date calculator is completely free with no sign-up, no login, and no hidden fees. The tool runs entirely in your browser — your data never leaves your device.
How do you calculate a due date after IVF?
For IVF, the due date comes from the embryo transfer date and the age of the embryo, not from your last period. ACOG Committee Opinion 700 gives the rule: add 261 days to a day-5 blastocyst transfer date, 263 days to a day-3 embryo transfer date, or 266 days to the egg retrieval (fertilization) date. The due date your fertility clinic assigns always takes priority.
Is an IVF due date more accurate than an LMP due date?
Usually, yes. With IVF the exact age of the embryo is known, so there is no guesswork about when ovulation happened or how long your cycle is. That is why ACOG recommends using the ART-derived gestational age to assign the due date for pregnancies conceived with assisted reproductive technology, instead of the last menstrual period.