Calculating Paint and Wallpaper
Estimating Wall Paint
- Add the length of each wall together.
- Multiply the total length of the walls by the ceiling height (this is the wall area).
- Subtract the square feet of the openings from the total wall area.
- Divide the remaining square feet by 350* to determine the number of gallons needed and increase this number by the amount of coats you plan to apply. (*Use the table below or check your paint can.
p>Example: Applying two coats, how many gallons of paint will you need for a room that is 12 x 14 with 9' ceilings? (Note: Total square foot of openings is 45).
- 12 + 12 + 14 + 14 = 52
- 52 x 9 = 468
- 468 - 45 = 423
- 423 / 350 = 1.21 x 2 coats (you need 2.5 gallons of paint)
Pratte Construction uses Premium Sherwin Williams coatings

Estimating Trim Paint
- Add the total linear feet of trim.
- Multiply the total length by .5 (or the exact width of trim).
- Divide by 350.
Estimating Ceiling Paint
- Multiply length of room by the width of the room to find ceiling area.
- Divide the area by 350.
Using the Table
- Identify your surface in the corresponding "exterior" or "interior" table.
- Divide your total area to be painted by the number in the first column.
- Add the "second" coat. (if needed)


Wallpaper
Using the Formula

- Add the total linear feet of walls.
- Multiply the total linear feet by the ceiling height for the total area.
- Divide the area by 30
Using the Table

- Add the length of each wall together (Total Linear Feet).
- In the first column, identify the closest "total perimeter" and round up.
- Identify the corresponding number based on your ceiling height. (this is the number of rolls you will need.
Use This Menu to Locate More Tips for Everyday Math
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