1. Determine the riser and the number of treads. Divide the floor to floor height for a fixed number (200) that is the average riser for the calculation. For example: 3200/200= 16 The result corresponds to the number of treads with staircase arrival at the same level of the floor. In case of arrival under slab, the number of treads will be lower (minus 1). 2. Choose the shape of the well according to the customer needs, between the available ones. 3. Determine the stair?s width according to the well, considering the hand?s passage (width of the well minus 5 cm). Determine the stair?s development according to the number of treads multiplied for the useful tread. The calculation is referred to traditional stairs, modular stairs, Kit stairs.