You’ve picked the perfect paint color and are ready to get started. Before you begin painting, you’ll need to estimate the amount of paint you’ll need. Here’s an easy four step process to find the square footage of your room and translate it to gallons.
Step 1: Add together the length of each wall to find the perimeter of the room.
15 + 20 + 15 + 20 = 70 feet
Step 2: Multiply the perimeter (70 feet) by the wall height to find the total wall area.
70 x 8 = 560 square feet
Step 3: Subtract the area of the windows and doors to find the actual amount of wall area you’re painting. You can figure 20 square feet for each door (20 x 2 = 40) and 15 square feet for each window (15 x 3 = 45). This gives you the total wall area to be painted.
560 – 85 = 475 square feet
Step 4:
Divide the total wall area by 350 (the average square-foot coverage in each gallon can) to find the number of gallons of paint you need. 
475 ÷ 350 = 1.4
-If the remainder is less than .5, order a couple of quarts to go with the gallons.
-If the remainder is more than .5, order an extra gallon.
-When in doubt round up, not down! You can always return unopened cans of paint.
For this example, you want to buy 1 gallon and 2 quarts of paint for a single coat. If you plan on applying a primer coat or multiple finish coats, multiple the results accordingly.
Tip! The average gallon of paint covers 350 square feet but you should always check the manufacturer’s specific recommendations and guidelines.Tip! For more information on paint colors and painting tips, we suggest the Sherman Williams website.
