The Pregnancy Calculator provides an estimation of how long you have been pregnant based on the date you enter for your last normal menstrual period. You should not view this as medical advice, because a missed period does not necessarily mean that you are pregnant, and having a period like bleeding does not mean you are not pregnant. If your period has been late, early, shorter than normal, and/or longer than normal you may have been having bleeding during pregnancy. Only an exam or pregnancy test can confirm pregnancy and only an ultrasound can determine approximate length of pregnancy. This calculator should only be used as a guide and should not be relied upon for weeks of pregnancy, conception date, or due date.