You have the following functions:

First The calculation of the reinforcement bars:

With just one click away, you can calculate the cross-sectional area of reinforcement bars, if you specify the diameter and the number of rods.

You know, however, the required cross-sectional area, which is fulfilled and the desired diameter, so you can stick with the function erf number, the number of rods needed for this cross-sectional area, can be calculated.

Second The calculation of the area reinforcing:

This feature allows you to calculate the cross-sectional area of a surface reinforcement, if you specify a diameter and bar spacing.

You know, however, the required cross-sectional area, which is fulfilled and the desired diameter, so you can stick with the function erf distance the distance at which the reinforcement must be inserted, can be calculated.