Conception Date Calculator

This calculator estimates when conception likely occurred, working either backwards from a due date or forwards from the first day of your last menstrual period, two of the most common starting points. Many people want to know their conception date out of curiosity, to understand the timeline of a pregnancy, or to relate it to events, travel or dates that matter to them. The estimate relies on the standard way pregnancy is dated. Conventionally, pregnancy is counted from the first day of the last menstrual period, and a full-term pregnancy is about 280 days, or 40 weeks, from that day. Conception, however, happens at ovulation, which is typically around 14 days after the last period begins, so conception is usually about 266 days before the due date. Because ovulation timing varies from person to person and cycle to cycle, conception is best thought of as a window of a few days rather than a single exact day. You choose whether you are working from your due date or your last period, enter the date, and the calculator estimates your conception date, a conception window of roughly five days around it, and the related date, either the estimated due date or the last period, to complete the picture. Use it as an interesting and useful guide, bearing in mind it is an estimate built on average cycle assumptions. Dating scans, especially an early ultrasound, give a more accurate picture and are what your midwife or doctor will rely on, particularly if your cycles are irregular or you are unsure of your dates. This tool is for general information and is not a medical dating of your pregnancy.

An estimate based on average cycle timing. Conception is a window, not an exact day. An early dating scan is more accurate. Not medical advice.