stepper motor calculation

The speed of a stepper is determined by the number of pulses delivered at the controller. The weight of the load will determine the size or gear ratio.

A popular stepper steps at 1.8 degrees steps. that implies 200 steps per revolution. If 1/2 steps are used 400 steps per revolution.

Micro-stepping is also available but at a lower torque.

If Your load is swiveled through the centre of gravity the effect of weight is minimized.

Hope this will assist. Feel free to supply more info.