To determine how many gallons of paint you need, follow these steps:
- Measure the walls : Measure the length of each wall and add them together to get the total perimeter in feet. Then measure the height of the walls in feet.
- Calculate total paintable area : Multiply the total perimeter by the height to get the total square footage of wall space.
- Subtract non-paintable areas : Subtract 20 square feet for each door and 15 square feet for each window to exclude these areas from your calculation.
- Divide by coverage per gallon : One gallon of paint typically covers about 400 square feet for one coat. Divide your total paintable square footage by 400 to find how many gallons you need for a single coat.
- Adjust for number of coats : Multiply the number of gallons by the number of coats you plan to apply (usually two coats for best coverage).
Example :
For a 12x12 room with 8-foot ceilings, two windows, and one door:
- Perimeter = 12 + 12 + 12 + 12 = 48 feet
- Height = 8 feet
- Total area = 48 x 8 = 384 sq ft
- Subtract doors/windows: 384 - 20 (door) - 30 (2 windows) = 334 sq ft
- Paint needed for one coat = 334 / 400 ≈ 0.84 gallons
- For two coats = 0.84 x 2 ≈ 1.7 gallons (round up to 2 gallons)
Additional tips :
- For rough or textured walls, or drastic color changes, you may need more paint or additional coats.
- A quart covers about 100 square feet, useful for small projects.
- Always round up to avoid running out mid-project.
- Use online paint calculators from paint brands or stores for more precise estimates.
In summary, the general rule is one gallon of paint covers about 400 square feet per coat , and you calculate gallons by dividing your total paintable square footage by 400, then multiplying by the number of coats
