Paint Calculator
How much paint do you actually need? Free, instant, and private — everything runs on your device.
For bare drywall, big repairs, stains, or drastic color changes
Mid-range wall paint runs $30–$55
350 typical; lower for textured walls
Your paint estimate
- Wall area (after openings)
- 301 sq ft
- Total to cover (2 coats)
- 602 sq ft
- Exact usage
- 1.72 gallons
- Estimated paint cost
- $89
Rounded up to real can sizes (quarts cost about 45% of gallon price). Keep the leftover quart for touch-ups, and note the color and sheen on the lid.
Buying paint by guesswork usually ends one of two ways: a second trip to the store mid-project, or two half-empty cans in the garage for the next decade. This calculator ends the guessing. Enter your room's measurements, subtract the doors and windows you won't be painting, choose your number of coats, and you'll see exactly how many gallons to buy — plus what it will cost.
The math uses the industry-standard coverage rate of about 350 square feet per gallon and rounds up to real can sizes, because paint stores don't sell you 1.3 gallons. If you're painting fresh drywall or making a dramatic color change, switch primer on and the calculator adds it for you.
How it works
No black box — this is the exact math the calculator runs.
- Wall area = 2 × (length + width) × ceiling height, in square feet.
- Each standard door subtracts 21 sq ft; each window subtracts 15 sq ft.
- Ceiling area (optional) adds length × width.
- Gallons = (paintable area × coats) ÷ coverage per gallon (350 sq ft default), rounded up to practical can sizes.
- Primer is calculated at one coat over the same area at 300 sq ft per gallon.
- Cost = gallons × your price per gallon, so you can compare paint lines before you commit.
Last reviewed July 24, 2026 · Paint & Decor
Frequently asked questions
How much paint do I need for a 12x12 room?
A 12×12 room with 8-foot ceilings has about 384 sq ft of wall area. After subtracting a door and two windows and applying two coats, you'll need about 2 gallons of wall paint. Add roughly 1 gallon if you're also painting the ceiling.
Does one gallon of paint really cover 350 square feet?
On smooth, previously painted walls, yes — 350–400 sq ft per gallon is typical. Textured, porous, or unprimed surfaces absorb more paint and can drop coverage to 250–300 sq ft. If your walls are rough, lower the coverage number in the calculator.
Should I buy extra paint beyond the estimate?
Keep about a quart for touch-ups. The calculator already rounds up to real can sizes, which usually builds in that buffer. Note the brand, color, and sheen on the can lid so you can match it years later.
Do I need two coats of paint?
Almost always. One coat rarely hides the old color evenly, even with 'one-coat' paints. The exceptions: repainting with the identical color, or applying over a tinted primer matched to your new color.