What is the circumfrences of a circle measured 4.5 ft.?

If your measurement of 4.5 feet is the diameter of the circle, then the circumference equals 4.5 times pi. Pi is a never ending number, but with only 3 or 4 decimal places, you can get pretty accurate answers. Pi is approximately equal to the number 3.14159265. In this case, 4.5 x Pi = 14.1372, more or less, and that is the size of the circle's circumference.