Estimate the expected delivery date from last period, conception date, ultrasound scan, or IVF embryo transfer.
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Health — Pregnancy
The estimated due date (EDD) — also called the estimated date of delivery — is a central reference point in antenatal care. This calculator estimates your EDD from your last menstrual period, conception date, ultrasound scan measurements, or IVF embryo transfer details.
The estimated due date (EDD) is the projected date at which a pregnancy reaches 40 weeks of gestational age. Most births occur within two weeks either side of the EDD — it is a statistical average, not a precise prediction. Only about 5% of babies are born on their exact due date.
Last menstrual period (LMP) — Naegele's rule: EDD = LMP + 280 days. If your cycle is longer or shorter than 28 days, the date adjusts accordingly. Conception date: EDD = conception + 266 days (38 weeks from fertilisation). Ultrasound scan: EDD is back-calculated from gestational age at scan; scan date minus gestational days gives an LMP equivalent, then EDD = LMP equivalent + 280 days. IVF transfer: LMP equivalent = transfer date minus (14 + embryo age in days); for a day-5 blastocyst transfer this is 19 days before transfer.
Early ultrasound scanning (8–13 weeks) is more accurate than LMP-based dating, especially for women with irregular cycles. Most antenatal services revise the EDD after the booking or dating scan. The scan-derived EDD becomes the clinical reference point for the remainder of pregnancy.
Frequently asked questions
Naegele's rule calculates EDD as LMP + 280 days (40 weeks). It assumes a 28-day cycle and ovulation on day 14. For cycles other than 28 days, the EDD is adjusted by the difference from 28.
Only about 5% of babies are born on their exact due date. The EDD is a 40-week statistical average — most births occur between 38 and 42 weeks. It is most useful as a planning reference, not a fixed target.
With IVF, the exact transfer date and embryo age are known, allowing a more precise EDD calculation. A day-5 blastocyst transfer is equivalent to day 19 of a natural cycle, so the LMP equivalent is 19 days before the transfer date.
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Estimate your pregnancy due date from your last period or conception date, with gestational age and trimester timing.
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Estimate conception date and fertile window from your last menstrual period and cycle length, or work backwards from a known due date.
