Paint Calculator
Estimate paint for any room. Enter the wall dimensions, subtract windows and doors, choose your number of coats, and get the paintable area, gallons required, and an estimated cost.
Your project
Estimate
Paint needed · Rounded up to whole gallons
- Paintable wall area
- 333ft²
- Estimated paint cost
- $76.00
Estimates are guidance only and exclude tax, labor, and site conditions unless stated. Confirm with a local pro.
How it's calculated
No black boxes — here is the exact math behind your estimate, so you can check it or adapt it for your own quote.
- 1
Wall area = 2 × (length + width) × height - 2
Openings = windows × 15 + doors × 21 - 3
Paintable area = wall area − openings - 4
Gallons = ⌈ paintable × coats ÷ 350 ⌉
Worked example
A 12 ft × 12 ft room with 8 ft walls, 2 windows, 1 door, painted with 2 coats.
Inputs
- Room length
- 12 ft
- Room width
- 12 ft
- Wall height
- 8 ft
- Windows
- 2
- Doors
- 1
- Coats
- 2
- Price per gallon
- 38 $/gal
Result
- Paint needed
- 2 gal
- Paintable wall area
- 333 ft²
- Estimated paint cost
- $76.00
Tools & materials for this project
As an Amazon Associate we may earn from qualifying purchases, at no extra cost to you.
- Paint roller & tray kit A roller frame, covers, and tray for interior walls.
- Painter's tape Mask trim and edges for clean lines.
- Canvas drop cloth Protect floors and furniture while you paint.
Compare local pros for paint
An estimate gets you a budget. A few competing quotes get you the real price. Tell us about the job and we'll help you find vetted contractors nearby.