The sale and measurement of genuine leather typically follow these methods and units:

Sale Methods:

Genuine leather is usually sold by area rather than by yard or yards. This is because leather is a natural material and does not have neat edges like other fabrics; the size of each piece of leather is limited by the size of the animal from which it came.

Large leathers, such as cowhide, are often measured in square meters (m²). Sometimes, square decimeters (dm²) are also used for representation.

In the field of clothing, sheepskin, pigskin, and goatskin are usually measured in square feet or square inches.

Measurement Units:

The thickness of leather can be measured in millimeters (mm) or ounces (oz). Ounces are the most commonly used measurement unit in North America, while millimeters are the most popular standard worldwide.
One ounce of leather is equal to 1/64 of an inch (approximately 0.4 millimeters).

The weight of leather can also be expressed in ounces, which is often used to describe the weight or texture of certain types of leather, such as furniture and bag leather. Theoretically, one square foot of leather will have a certain weight and thickness; therefore, 3-ounce leather theoretically refers to leather that weighs 3 ounces per square foot.

Unit Conversion:

The conversion factor from square meters to square feet is 10,764, and from square meters to square inches is 155,000.
For example, 2.95 square meters multiplied by 10,764 equals 31.75 square feet; 45 square feet divided by 10,764 equals 4.18 square meters.

Additional Notes !!!:

The thickness of leather can vary due to factors such as the tanning process, the way the leather is split, original scars and blemishes, and the chemicals used in the tanning process.
The thickness of leather is usually given as a range, such as 2-3 ounces, to account for these variations.
These are the common methods and units used for the sale and measurement of genuine leather, as well as the conversion relationships between them.