[header] How to calculate price per square foot for house painting [title] Calculate for house painting by multiplying the length by width of the room or rooms that you want to paint. [substeps] Add the individual sums together. [title] Measure the height and width of each door and each window in a room to be painted. 
[substeps] Multiply height by width to find the square footage of each door and window. Combine the totals for each door and window to calculate for house painting.