Use the correct type of tape measure. When taking body measurements, you need to use the correct type of tape measure. You will want to use a soft cloth or flexible plastic/rubber tape measure, such as is used in sewing. Do not use a metal measuring tape such as is used in construction (it will be inaccurate).
Measure correctly. You want to be sure that when you measure, the tape is straight and in line with the appropriate body part. For example, for most circumference measurements the tape will need to be parallel to the floor while while lengths will need to be either parallel or perpendicular (based on the line orientation of the body part being measured).Also, please leave one finger space.
Wear appropriate clothing. You can’t get a very accurate measurement when wearing baggy or thick clothing, so try to wear clothes which fit closely or wear nothing at all. Similarly, breast measurements for women will be most accurate when wearing a well-fitting, unpadded bra.