The work aims to study the method used to measure the contact area (S) and the volume of food simulants (V) of different shapes of food contact materials and products. For the detection of food contact materials and products, generally S and V should be accurately determined; however, due to the diversity of the sample structure and the tester's unfamiliarity with the calculation formula of S and V during the actual detection, the estimation method was often used to calculate them, which usually led to a larger human error. Taking some stainless steel products as an example, the mathematical manuals at home and abroad were retrieved to find out the relevant formulas for derivation. In the meantime, the method used to measure the irregular geometric bodies S and V was synthesized. The surface area and volume formula of common regular geometric body, such as torus, helical spring, spherical segment, ellipsoid, barrel shape, paraboloid and so on, as well as the method used to measure the irregular geometric bodies S and V were obtained. By using these formulas and methods, it is easy to calculate accurately the S and V and reduce human error, which lays the foundation for scientific and accurate detection.