In order to choose the adequate size of a V-Belt the values you need to know are:
The V shape of the belt tracks in a mating groove in the pulley (or sheave), so that the belt cannot slip off. The belt also tends to wedge into the groove as the load increases – the greater the load, the greater the wedging action – improving torque transmission and making the v belt an effective solution. They can be supplied at various fixed lengths or as a segmented section, where the segments are linked (spliced) to form a belt of the required length.
For high-power requirements, two or more v-belts can be joined side-by-side in an arrangement called a multi-V or banded belt, running on matching multi-groove sheaves. The strength of these belts is obtained by reinforcements with fibers like steel, polyester or aramid.