well, if you want to measure the length, just stretch the tape and measure it. If you want to measure the diameter, measure the circumference of the screw, then divided by 3.1415, then you will get the diameter.
If you have a tape measure that measures in inches. First convert the inches to decimal inches. So 1-15/16" would be 1 + 15/16 or 1.9375. Next multiply that number by 2.54 to get centimeters. So...
Measure human height by the transitive property. Stand up against the wall and make a mark at your height. Then measure the distance from the floor to the mark. You are as tall as the mark is above...
From personal experience, it is innacurate. For me I got my height measured as 5'10 at the doctors, but when I measure myself at home with a tape meter it says I am 5'9, a full 2.50cm difference.