How to calculate quantities using REVIT Software?

By reading your question I'd say you are referring to BoQs but not to BoMs which are slightly different in Revit. It is true that the both fell under the Schedules "category". In short, if it is in the model you can Schedule more or less any element. You may also add formulas or edit parameter values directly in the Schedule for your convenience. This, the schedule you're creating can be a good starting point for your BoQs. In most of the projects I worked Microsoft Excel also came into picture in order to finalize the BoQs.

For the elements that are not modeled you may use now Navisworks which offers quite a lot of flexibility for these tasks. I find the QTO functionality of Navisworks almost fit for purpose already but it will be interesting to see what other future enhancements Autodesk is going to implement in this area.

First you need to make a schedule & add the type of materials you want to calculate the quantity. Then you choose the parameters that you want the program to follow & you're done.