Donato Bramante was known as a classically trained architect, but there are so many principles to follow that we may not understand his basics. This research explores some of his works to see which proportioning rules he followed and hopefully find a reason for why he broke these rules. The process was done by diagraming over the elevations, floor plans, etc. to see which of the following proportion methods he used: The Vitruvian Man and the Golden Section. The structures that were used for this testing are as follows: Tempietto in Rome, St. Peters Basilica, and the Palazzo Caprini. My findings were that Bramante followed both of these methods but switched it up per building depending on the shape. A circular building would use the Vitruvian Man method while a rectangular building would use the Golden Section. But depending on the shape he would repeat the chosen shape in the floor plan. Some of his rules of proportion were broken due to matching surrounding buildings or to have continuity of window widths between floors. But with this research we can better understand how classical buildings were designed and use these same proportioning methods in our future along with finding where and when we can break the rules.