text: does the no. of belt or its length in belt drive have something to do with speed computations?   length has nothing to do with the belts speed of course. length only makes sure they reach all pulleys involved. the speed of any belt is based on diameter of the pulleys they turn and the driving forces (drive pulley) to the belt. of course the more or wider belts you have the better the grip to the pulleys if high torgue loads on the pulleys are expected.