Add 266 days (38 weeks) to the conception date. Because gestational age is measured from the last menstrual period — about 14 days before conception — that is the same EDD as 280 days from LMP. This calculator does the conversion for you.

Almost. Conception happens when the egg is fertilised, which is within about 24 hours of ovulation. The egg is only viable for around a day, so your ovulation date and conception date are effectively the same for dating purposes.

The standard estimated due date (EDD) is 40 weeks (280 days) from the first day of your last menstrual period (LMP) using Naegele's rule. If you know your conception date, IVF transfer date, or a scan-dated gestational age instead, this calculator works backwards from those to the same EDD. Only about 5% of babies are born on their exact due date — most arrive within two weeks either side.

EDD stands for Estimated Due Date — the date your baby is expected to arrive, calculated as 40 weeks from your last menstrual period. It is an estimate, not a deadline: a normal, full-term birth can happen any time from 37 to 42 weeks.

A first-trimester ultrasound (crown-rump length, ideally before 14 weeks) is the most accurate way to date a pregnancy and is what doctors use to confirm or revise the due date. LMP dating is reliable only if your cycles are regular and you remember the date. For IVF, the transfer date gives a very precise due date because the day of fertilisation is known.

First trimester: weeks 1–12. Second trimester: weeks 13–26. Third trimester: weeks 27–40. This calculator shows your current trimester, your week-by-week progress, and key appointment milestones such as the NT scan (11–13 weeks) and anomaly scan (around 20 weeks).

Gestational age is counted from the first day of your last period, not from conception — so you are already counted as about 2 weeks pregnant at the moment of conception. Enter your date above and the calculator shows your current weeks and days, your trimester, and how many weeks remain.