بسم الله الرحمن الرحيم
(Fatwa: 815/780/SN=11/1436)
You should have explained the nature of business which would have made it easy to write the method of calculation. However, whatsoever cash, recoverable debts and business materials (it includes raw material, ready materials, in case it is a shop then all types of saleable materials in the shop) after deducting debts if any, in case they reach equal to 52.5 tola (612 gram and 360 milligram) silver or more then you will have to pay 2.5% of all the total as zakah provided on completion of one year.
Note: In the saleable materials the selling price shall be final. It has nothing to do in how much price the material was ready or was bought. It should also be noted that zakah is not wajib on building, machinery, equipments and likewise other solid things. It would be better that you calculate it with any reliable Alim when you are going to pay the zakah.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband