IVF pregnancies have the most precise due dates because the date of fertilisation is known. Clinics still express the pregnancy in gestational weeks from an equivalent last period so that it matches standard charts.
How to use the IVF Due Date Calculator
- Embryo transfer date
- Embryo age at transfer
Results update as you type, and every field accepts the units shown in its menu.
How it works
Enter the transfer date and choose the embryo age. For frozen transfers use the embryo’s age when it was frozen.
Inputs explained
| Field | What to enter |
|---|---|
| Embryo transfer date | A date |
| Embryo age at transfer | Choose one: Day 3 embryo, Day 5 blastocyst, Day 6 blastocyst |
What each result means
- Equivalent LMP = [Embryo transfer date] – [Embryo age at transfer] – 14
- Due date = [Equivalent LMP] + 280
- Weeks pregnant today = floor([Days pregnant]÷7)
- …plus days = mod([Days pregnant], 7)
- Typical first blood test (beta hCG) = [Embryo transfer date] + 14 – ([Embryo age at transfer] – 3)
- First ultrasound (about 6–7 weeks) = [Equivalent LMP] + 45
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
Due date = transfer date + 266 days − embryo age (days)
(Day 5 transfer: + 261 days; day 3 transfer: + 263 days)
Equivalent LMP = transfer date − embryo age − 14 days
Worked example
Inputs — Embryo transfer date: 2026-09-15; Embryo age at transfer: Day 5 blastocyst.
Results — Equivalent LMP = Thu, August 27, 2026; Due date = Thu, June 3, 2027; Weeks pregnant today = 9 weeks; …plus days = 2 days; Trimester = First trimester; Typical first blood test (beta hCG) = Sun, September 27, 2026; First ultrasound (about 6–7 weeks) = Sun, October 11, 2026.
Key terms
- Naegele's rule
- Due date = first day of last period + 280 days (40 weeks).
- Gestational age
- Pregnancy length counted from the first day of the last period.
- Trimester
- One of three periods of pregnancy: weeks 1–13, 14–27 and 28 to birth.
Frequently asked questions
Why add 266 days?
Pregnancy lasts about 266 days from fertilisation (38 weeks).
Is a frozen embryo transfer calculated differently?
No – use the embryo's developmental age at transfer.
When should I test after transfer?
Clinics usually do a blood test 9–14 days after transfer.