Mobile – Since the invention of smartphones, the invention of applications to add to the phone has also helped doctors. As a nurse, when a patient comes to my floor and states she may be in labor, I pull out my mobile device and all I have to do is add the due date and it will calculate everything for me, from the due date to the last period, how much the size of the fetus and the gestational age at that time. Examples of these types of applications are Perfect OB Wheel, Gest Age, and The OB Wheel Pro http://appcrawlr.com/ios-apps/best-apps-gestational-age Computer websites: Websites are available to the patient and doctors see what might develop on the fetus and also the due date. Example of computer sites http://www.prokerala.com/health/pregnancy/pregnancy-wheel/ http://www.babymed.com/pregnancy-wheel handheld - The typical embodiment of this device is a piece of paper circular, plastic or metal between 4 inches and 10 inches in diameter. This was the root of gestational stones, until technology came along. These wheels are always available in labor and delivery units and gynecology offices for quick calculation when