Escenvir is the app, where you can do a chemical calculation in your daily needs. Lbs of Chemical / Gal of Solution and Tank Volume Calculations is very important in a chemical calculation. For Lbs of Chemical / Gal, this calculator will give you the lbs. of the chemical in a gallon of a solution when you enter the strength of the chemical and the specific gravity. For Tank Volume Calculations, you have to give the value of length, width & side water depth. You will get the result of cubic feet and gallons.