This calculator uses formulas to automatically calculate variable costs based on SF, # of bathrooms, stories, grade, year built, and pool. It also has some fixed costs built into it. The way you use it is in a binary format - For example, if you know you need to do interior painting, type "1" in the blue box and that cell will populate as a cost. The spreadsheet already knows the cost because it estimates the interior painting based on SF. If interior painting is not needed, leave blank or type "0". (Also, if you are only painting half the house, type "0.5")   **This calculator is only as good as the assumptions that are plugged in and even then, should not be solely relied upon. It's only good for providing a ballpark estimate.