Builders Calculator

I need someone to create an android app to assist dyi builders to calculate materials needed for basic building projects. I have attached a rough flowchart of the screens and here follows a breakdown of the formulas used. 1) build a wall: Square meter of wallr: height in meters x length in meters (minus height x length of doors and windows) (x2 for double wall) Bricks = square meter x 55 cement = bricks/1000 x 3.5 = bags (need to round up) sand = bricks/1000 x 0.5 = cubes Brick Force = height/0.3 x length = Meters 2) Plaster a wall Square meter of wallr: height in meters x length in meters (minus height x length of doors and windows) (x2 for both sides) Cement: square meters/10 = bags (round upf) Plaster Sand: square meter/100 x 1.7 = Cubes 3) Pour Foundation Cubic Meters ; width x Depth x length Cement: Cubes x 6.4 = Bags ( Round up) Sand: Cubes x 0.66 = Cubes Stone : Cubes x 0.78 = Cubes Fairly basic app. We will need to be able to change the formula values fairly easily. Thanks