Conception date calculator
An estimate with a genuine margin of error of several days. Sperm survive up to five days, so conception can occur well after intercourse. This should never be treated as establishing a date of conception for any purpose that matters.
Conception is estimated as roughly two weeks after the last menstrual period, or 266 days before the due date. The margin of error is several days, because ovulation timing varies and sperm survive up to five days.
How to estimate a conception date
The uncertainty is larger than the single date suggests, and it runs in two directions. Ovulation can shift by several days from cycle to cycle even in regular cycles. And because sperm survive up to five days, intercourse well before ovulation can result in conception on the day of ovulation itself — so the date of conception and the date of intercourse are frequently different. Any use of this figure that assumes precision is misusing it.
Questions
About 266 days before the due date, or roughly two weeks after the last period started.