Due Date Calculator
Calculate your estimated due date using three methods: last menstrual period, ultrasound gestational age, or IVF transfer date.
| Week | Date | Milestone | Status |
|---|---|---|---|
| Enter your details to see milestones | |||
Estimate your due date three different ways — from your last menstrual period, an ultrasound measurement, or an IVF embryo transfer date — whichever information you have available.
How Due Date Calculator Works
The LMP method applies Naegele's rule (due date = LMP + 280 days), adjusted for cycle lengths other than 28 days. The ultrasound method instead works backward from a measured gestational age at a specific scan date: estimated LMP = ultrasound date − (weeks + days measured), then adds 280 days from that point — useful when your LMP is uncertain, since early ultrasound dating is often considered more accurate than menstrual-history dating.
The IVF method is built for known transfer dates: due date = transfer date − days-past-ovulation (DPO) at transfer + 266 days. A standard day-5 blastocyst transfer, for instance, is treated as 5 days past ovulation, so the calculator subtracts 5 days before adding the standard 266-day gestation length used from ovulation.
All three methods, when accurate for the same real pregnancy, converge on the same due date — the calculator simply gives you flexibility to use whichever data point (LMP, scan, or transfer date) you actually have on hand.
See It In Action
Who Uses Due Date Calculator and Why
- Comparing due date estimates from LMP, an ultrasound measurement, and an IVF transfer date to see how closely they agree.
- Getting the most reliable available due date estimate when LMP memory is uncertain but an ultrasound scan result is on hand.
- Calculating a due date from a known day-3 or day-5 embryo transfer date for an IVF pregnancy.
Mistakes to Avoid
- Mixing up a day-3 and day-5 transfer when using the IVF method — the days-past-ovulation value used in the calculation depends on which type of transfer occurred, and getting it backwards shifts the due date by two days.
- Assuming the ultrasound method and LMP method should always agree exactly — if your cycle isn't a standard 28 days or ovulation didn't happen exactly on day 14, they can genuinely differ by several days, and the ultrasound is usually considered more reliable in that case.
Tips for Best Results
- If you have an early ultrasound measurement, that method is generally considered more accurate than LMP alone, particularly with irregular cycles.
- For an IVF pregnancy, the transfer-date method is typically the most precise of the three, since the embryo's exact age is known rather than estimated.
Fixing Common Problems
The three methods gave me different due dates. — A difference of a few days is common and usually reflects genuine uncertainty in LMP-based dating rather than a calculation error — when available, the ultrasound or IVF transfer date methods are generally considered more reliable than LMP alone.
Terms Explained
DPO (Days Past Ovulation): How many days after ovulation an embryo was at the time of transfer — 3 for a day-3 transfer, 5 for a day-5 (blastocyst) transfer — used to adjust the due date calculation for IVF pregnancies.