how many days off do the conception calculator be off if you have a 28/29 day cycle?

Answer 1

I would say about a week for most people but it could really be off by almost a month, because even though most calculators are based on a 28 day cycle. The calculator does not know when you ovulated. It estimates that time to be on the 14th day, but average is anywhere between nine and 14, and you may not be average it is absolutely possible to ovulate at any point during the cycle

Answer 2

Well sperm can live inside you for 7 days so maybe the day you had sex is not the day you got pregnant. The sperm may have not fetilized the egg until a few days later.