How much does a gallon of paint cover?

About 350–400 sq ft per coat on smooth walls. Textured or porous surfaces cover less.

Do I need one coat or two?

Two coats is standard for durable, even color — especially over a different base color or fresh drywall.

Should I buy extra paint?

Yes, keep 5–10% extra for touch-ups and to ensure a consistent dye-lot match later.

Paint Cost Calculator

Use the paint cost calculator below to get an instant material and installed price range for your project. To estimate paint, find the wall area (perimeter × height), subtract about 21 sq ft per door or window, multiply by the number of coats, and divide by 350 (sq ft per gallon). A 12×12 ft room with 8 ft walls needs about 2 gallons for two coats, costing roughly $50–$120.

Your measurements

Room length(ft)

Room width(ft)

Ceiling height(ft)

Coats

Doors & windows

Each opening subtracts ~21 sq ft of wall.

Price per gallon/liter($/gal)

Enter your measurements

Fill in the fields to see your estimate.

Paint needed by room size

Gallons for two coats on a room with 8 ft walls, minus two openings.

Room size	Wall area	Gallons (2 coats)	Paint cost
10 × 10 ft	~318 ft²	~2 gal	$50 – $120
12 × 12 ft	~342 ft²	~2 gal	$50 – $120
15 × 15 ft	~438 ft²	~3 gal	$75 – $180
20 × 20 ft	~598 ft²	~4 gal	$100 – $240

What affects paint cost

Project size — larger painting jobs lower the cost per unit but raise the total.
Material grade — premium products cost more but often last longer.
Labor rates — local wages and demand swing installed prices significantly.
Region — prices vary by state and metro (see local cost pages below).
Site access & prep — removal of old material and difficult access add cost.
Season — booking in the off-season can cut labor pricing.