Pregnancy Due Date Calculator

A due date calculator answers the first question almost everyone asks after a positive test: when is the baby likely to arrive? This tool estimates the expected date of delivery using Naegele’s rule — the standard method used in prenatal care: 280 days (40 weeks) are counted from the first day of your last menstrual period. Because that rule assumes a 28-day cycle, the calculator also lets you enter your average cycle length between 21 and 35 days and shifts the estimate accordingly, one day per day of difference.

If you know the exact day of conception, switch to the conception mode, which adds 266 days instead. After IVF, the timing is known even more precisely, so a dedicated mode counts from the embryo transfer date and the embryo’s age at transfer — 261 days for a day-5 blastocyst or 263 days for a day-3 embryo. Whichever method you choose, the result updates instantly as you type, with no button to press.

Beyond the due date itself, the calculator shows your current week of pregnancy and trimester when the start date is in the past, and lays out four key milestone dates: the end of the first trimester at 12 weeks, the mid-pregnancy anatomy scan around 20 weeks, the start of the third trimester at 28 weeks, and full term at 37 weeks. These dates make it easier to plan appointments, screenings, and maternity leave.

All calculations run entirely in your browser: nothing is uploaded, tracked, or saved, so a very personal date stays on your device. Please remember that only about 4–5% of babies are born exactly on their estimated due date — most arrive within two weeks either side. This calculator gives an approximate estimate for orientation and is not medical advice; your doctor or midwife will refine the date, usually with a first-trimester ultrasound.