Interior Paint Calculator
An interior paint calculator finds how much paint a room needs by calculating wall area, subtracting doors and windows, and dividing by gallon coverage for your chosen number of coats. Enter your room length, width, height and openings below to get the gallons for interior walls.
Computes perimeter from length+width, then wall area.
- Paintable area
- 0 sq ft
- Coats
- 2
Enter your dimensions to see the gallons you need.
Estimate only. Material yields vary by product and brand; check your product label and add a margin.
How Much Interior Paint Do You Need for a Room?
To find interior paint for a room, calculate the perimeter (two times length plus two times width), multiply by wall height for total wall area, subtract doors and windows, then divide by 350 and multiply by coats. A 12 by 14 foot room at 8 feet high needs about 416 square feet of wall, roughly 2.4 gallons over two coats after openings. The calculator builds the perimeter from your room size automatically.
Do You Paint the Ceiling Separately?
Usually yes. Ceilings are calculated and often painted separately from walls, using flat ceiling paint, because the area and product differ. The interior calculator here covers walls; use the ceiling calculator for the ceiling area. Keeping them separate gives a more accurate paint order, since ceiling paint and wall paint are bought as different products.
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Frequently asked questions
- How much paint for a bedroom?
- A typical 12 by 14 foot bedroom with 8 foot walls needs about 2.4 gallons for two coats after subtracting a door and windows. Use the calculator for your exact size.
- Does interior paint include the ceiling?
- No, ceilings are usually calculated separately with flat ceiling paint. This calculator covers walls; use the ceiling calculator for the ceiling area.
- How do I calculate how much paint I need?
- Add up the wall area in square feet (perimeter times wall height) and divide by the coverage of one gallon, commonly around 350 to 400 square feet for one coat. Multiply by the number of coats and subtract large openings like doors and windows.
- How much does one gallon of paint cover?
- One gallon typically covers about 350 to 400 square feet in a single coat on a smooth, primed surface. Rough or porous walls absorb more and cover less, so plan for the lower end of the range and add primer separately.
- How much paint do I need for a 12 by 12 room?
- A 12 by 12 room with 8 ft walls has a 48 ft perimeter, so wall area is 48 x 8 = 384 sq ft. One coat is about 1.1 gallons, so two coats is about 2.2 gallons: plan on 2.5 gallons to have a small reserve for touch-ups.