Most likely conception date and fertile window, from your last period and cycle length.
It equates conception with ovulation day, calculated as LMP + (cycle length − 14), based on a standard 14-day luteal phase. This is the day conception is most likely, not a guarantee.
It's 14 days after the estimated ovulation date, roughly the point where a home pregnancy test is most likely to detect pregnancy hormone if conception occurred around ovulation.
Both use the same LMP + (cycle length − 14) formula and 7-day fertile window. This page frames the result around conception and testing, while the Ovulation Calculator also shows your next predicted period and current cycle day.