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. Subtract ~50 sq ft for a door and window, leaving ~334 sq ft. At 350 sq ft per gallon, you need about 1 gallon for one coat, or 2 gallons for two coats.

How many square feet does a gallon of paint cover?

One gallon of paint covers approximately 350–400 square feet on smooth surfaces with one coat. Rough or textured surfaces may reduce coverage to 250–300 sq ft per gallon. Primer typically covers 200–300 sq ft per gallon.

Do I need one coat or two coats of paint?

Two coats is standard for most jobs. You might get away with one coat if you're painting the same color over a well-prepared surface. Always use two coats when: changing from dark to light, painting over patched areas, or using a new color. Some premium paints advertise one-coat coverage, but professionals almost always do two.

Paint Calculator — How Much Paint Do I Need?

🎨 Room Dimensions

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Number of Coats

Doors (standard 21 sq ft)

Windows (standard 15 sq ft)

Surface Type

Include

Ceiling

Trim / Baseboards

—

Gallons (Walls)

—

Gallons (Ceiling)

—

Gallons (Trim)

—

Total Gallons

Breakdown

Total wall area—

Minus doors & windows—

Paintable wall area—

Coverage per gallon—

Coats—

Ceiling area—

Trim (linear ft)—

Estimated cost (wall paint)—

Pro Tip: Buy one extra quart as a touch-up reserve. Store it with the color code and room name written on the lid. You'll thank yourself in 6 months when you need to fix a scuff.

How to Estimate Paint: Contractor's Guide

The Basic Formula

Gallons = (Paintable Area × Coats) ÷ Coverage Rate

Paintable area = total wall area minus doors and windows. Standard coverage is 350 sq ft per gallon for smooth walls. Textured surfaces use 250–300 sq ft per gallon.

Paint Coverage by Type

Paint Type	Coverage (sq ft/gal)	Price Range
Flat / Matte	350–400	$25–$50
Eggshell	350–400	$30–$55
Satin	350–400	$30–$55
Semi-Gloss	350–400	$30–$60
High-Gloss	300–350	$35–$70
Primer	200–300	$20–$40
Exterior (latex)	250–350	$35–$70

Pricing Paint Jobs as a Contractor

Most painting contractors charge $2–$6 per square foot for interior painting, including labor and materials. A typical 12×12 room with 8-foot ceilings costs $800–$2,000 depending on complexity, prep work, and finish quality.

Labor: 60–70% of total job cost
Materials: 15–25% (paint, primer, tape, drop cloths)
Overhead & profit: 15–25%

Use a minimum 50% markup on materials and charge labor at $35–$65/hour per painter depending on your market.

When to Use Primer

Painting over bare drywall or patches (always prime)
Going from dark to light colors
Covering stains or smoke damage (use shellac-based primer)
Painting over glossy surfaces (scuff sand + prime)
New wood trim or cabinets

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