How much is 1.57 on American ruler?

On an American ruler, 1.57 inches would be just slightly over 1 and a half inches. It can be visualized as 1 inch and 5/8 inch, since 0.57 inches is approximately 0.57 x 16 = 9.12/16, or about 9/16 of an inch. Therefore, you would measure to the 1 inch mark and then a little past the 1 and 1/2 inch mark, close to 5/8 inch.