Torque is more important than wattage, because there is no gears. Now if we want to calculate the actual wattage of a direct drive, with 622mm rim and 25 km/h

Torque is more important than wattage, because there is no gears. Now if we want to calculate the actual wattage of a direct drive, with 622mm rim and 25 km/h and 23Nm, it is simply 3.14 x 0.622 x 25 x 1000 / 3600 x 23 311.95027777777784 Watts exactly -- 25km/h is the EU-maximum for electric bicycles, otherwise it is a moped or motorcycle.