FET Pregnancy Due Date Calculator
Use this due date calculator fet tool to estimate your baby’s due date using one of three methods: LMP, conception date, or IVF/FET transfer date.
For FET, due date = transfer date + (266 − embryo age in days).
What is a due date calculator fet?
A due date calculator fet is a pregnancy date estimator specifically designed for people who conceived through fertility treatment, especially frozen embryo transfer (FET). Unlike standard calculators that rely only on the last menstrual period, this method can use the exact transfer date and embryo age, giving a more precise estimate from day one.
Why FET due date estimates are usually more accurate
When conception happens naturally, ovulation can vary from cycle to cycle. That means LMP-based estimates are useful but not always exact. In IVF and FET cycles, your care team knows:
- the transfer date,
- the embryo development day (for example day 3 or day 5),
- and the medical timeline for implantation support.
Because those timing variables are known, due date projection from FET tends to be more consistent than LMP-only methods.
How the calculator works
1) LMP method
Estimated due date = LMP + 280 days (40 weeks).
2) Conception method
Estimated due date = Conception date + 266 days (38 weeks after fertilization).
3) IVF/FET method
Estimated due date = Transfer date + (266 − embryo age).
| Transfer Type | Days to Add to Transfer Date | Equivalent Formula |
|---|---|---|
| Day 3 embryo | 263 days | 266 - 3 |
| Day 5 blastocyst | 261 days | 266 - 5 |
| Day 6 blastocyst | 260 days | 266 - 6 |
How to use this due date calculator fet tool
- Select your method (LMP, conception, or IVF/FET).
- Enter the required date.
- If using FET, choose embryo age at transfer.
- Click Calculate Due Date.
You’ll see your estimated due date, estimated gestational age, and a full-term window range.
Understanding your result
Your due date is an estimate, not a guarantee. Most births occur within a range around 40 weeks. A normal full-term birth generally falls between 37 and 42 weeks. Your provider may refine dating if first-trimester ultrasound measurements suggest a different timeline.
When to trust clinical dating over calculators
Online tools are useful for planning, but your fertility clinic or OB team should guide final dating. They may adjust due date timing based on:
- early ultrasound crown-rump length,
- known IVF laboratory records,
- cycle-specific hormonal protocols,
- medical conditions affecting pregnancy monitoring.
Quick FAQ
Is FET due date the same as natural conception due date?
The biological pregnancy length is similar, but FET dating is often more precise because fertilization timing is known.
Should I use LMP if I had IVF?
Usually no. IVF/FET transfer date with embryo age is preferred when available.
Can due date change after ultrasound?
Yes. Your clinician may update dating based on early ultrasound if there is a meaningful difference.
Final note
This due date calculator fet page is for education and planning. It does not replace medical care. Always confirm your pregnancy timeline with your fertility specialist, obstetrician, or midwife.