Leather can be divided into large pieces and small pieces. Generally, it is cowhide over 40 feet, mostly sheepskin, pigskin or some special skins. I want to know what the warranty period of your factory is. Generally, my calculation method is that the size of a single sheet of paper is above 20cm*20cm, below 20%, below 10cm * 15cm. If it's too much trouble, you can make a large order of 10-20%, or a small order of 15-30%, for example, the row of knives for some small parts, with a large calculation area. However, some small rare skins, such as snake skin, ostrich skin, crocodile skin, pearl fish skin and carved skin, are all calculated according to theory, so the loss is not counted. Formula: (length * width * number of pieces) /( 144)* (above loss) = SF. No matter how advanced the formula is, it is useless, mainly in the calculation of loss, which requires familiarity with the inside of the factory!