How much paint do I need for a 12x12 room?

A standard 12x12 room with 8-foot ceilings has about 384 square feet of wall space. Since one gallon of paint covers approximately 400 square feet, you will need exactly one gallon for a single coat, or two gallons for the recommended two coats.

Should I use one coat or two coats of paint?

You should almost always use two coats of paint. Even high-quality 'paint-and-primer in one' products usually require two coats for full, even coverage and proper color depth, especially when rolling over drywall.

How much do painters charge per room?

Professional painters typically charge between $300 and $800 per average-sized room. This price varies based on the amount of prep work required (like patching drywall), the ceiling height, and the quality of the paint used.

Paint Area & Cost Calculator

Stop guessing at the hardware store. Enter your room dimensions below to find out exactly how much paint you need and what it will cost.

Room Dimensions (Feet)

Length:

Width:

Ceiling Height:

Deductions (Optional)

We subtract 20 sq ft for doors and 15 sq ft for windows.

Number of Doors:

Number of Windows:

Project Details

Number of Coats:

Cost per Gallon ($):

Your Results

Total Paintable Area:

0 Sq Ft

Gallons Needed:

(Based on 400 sq ft/gallon coverage)

Estimated Material Cost:

*Note: Calculations round UP to the nearest whole gallon, as paint cannot be purchased in fractions. Always mix multiple gallons of the same color in a large bucket (boxing) to ensure color consistency.

Painting is often the first step in a larger remodel. See how it fits into your overall plan by reading our Ultimate Home Renovation Guide.

The Transformative Power of Paint

There is no project in the world of home renovation that offers a higher return on investment than a fresh coat of paint. For a few hundred dollars in materials and a weekend of sweat equity, you can entirely change the mood, perceived size, and cleanliness of a room. Whether you are prepping a house for sale or making a new house feel like your own, painting is the ultimate budget-friendly upgrade.

However, the most frustrating part of painting isn't the actual rolling—it's running out of paint when you have one wall left to finish. Conversely, buying too much premium paint wastes money. Our calculator is designed to eliminate the guesswork so you can buy exactly what you need in a single trip.

How the Math Works

Calculating paint requirements is basic geometry, but it's easy to forget the specifics when standing in the hardware store aisle. The standard industry rule of thumb is that one gallon of high-quality interior acrylic latex paint covers approximately 400 square feet of smooth drywall. If your walls are textured (like heavy knockdown or popcorn), the coverage drops to roughly 300 to 350 square feet per gallon.

To find your total square footage, our calculator finds the perimeter of the room (Length + Length + Width + Width) and multiplies it by the ceiling height. From that total, we subtract the "unpaintable" spaces. A standard interior door accounts for roughly 20 square feet, and an average window accounts for about 15 square feet.

Why Two Coats Are Mandatory

You may be tempted to select "1 Coat" on the calculator to save money, especially if you are buying a premium "Paint and Primer in One" product. Professional painters rarely, if ever, apply only one coat of paint.

Color Depth: A single coat will almost always show "holidays" (industry slang for missed spots where the old color peeks through). Two coats ensure a rich, uniform color finish.
Durability: Paint acts as a protective skin for your drywall. Two coats create a thicker, more resilient barrier against scuffs, moisture, and fading.
Sheen Consistency: If you are using an eggshell or satin finish, a single coat will often dry with an uneven sheen, looking blotchy when the light hits it. The second coat evens out the finish.

The only time a single coat is acceptable is if you are painting a wall the exact same color and sheen it currently is, simply to freshen it up.

Understanding Paint Quality and Pricing

When you walk into a paint store, you will see gallons ranging from $20 to over $100. It is vital to understand what you are paying for.

Economy Grade ($20 - $30/gallon)

These paints have lower volume solids (the binders and pigments left behind after the liquid evaporates). They are thinner, require more coats to cover, and are prone to splattering off the roller. They are generally only used for ceilings, closets, or by house-flippers looking to cut extreme corners. You will likely spend more money buying extra gallons to achieve coverage than if you had bought better paint.

Contractor / Mid-Grade ($35 - $50/gallon)

This is the sweet spot for most DIYers. These paints (like Sherwin-Williams SuperPaint or Benjamin Moore Regal Select) offer excellent coverage, durability, and a smooth finish. They are thick enough to hide minor drywall imperfections and will reliably cover in two coats.

Premium Grade ($60 - $100+/gallon)

Premium paints (like Benjamin Moore Aura or Sherwin-Williams Emerald) utilize specialized resins and advanced color lock technology. They offer superior washability (you can scrub them without removing the finish), exceptional fade resistance, and the truest color rendering. They are excellent choices for high-traffic areas like kitchens and hallways, or for deep, dark colors (like navy blue or emerald green) that typically require four coats in cheaper brands.

Pro Tips for a Flawless Finish

Having the right amount of paint is only half the battle. How you apply it matters just as much.

Prep is Everything: 80% of a good paint job is preparation. Wash the walls with TSP (Tri-Sodium Phosphate) to remove grease, fill nail holes with spackle, sand the patches smooth, and tape your trim meticulously.
Box Your Paint: Even computer-mixed paints can have microscopic color variations between cans. "Boxing" means pouring all the gallons you purchased for a room into a single 5-gallon bucket and mixing them together. This guarantees an identical color match across all walls.
Maintain a Wet Edge: When rolling, work in 3x3 foot sections. Always roll back into the wet paint you just applied to avoid "lap marks" (visible lines where dried paint overlaps with wet paint).
Don't Skimp on the Tools: A $50 gallon of paint applied with a $2 roller cover will look terrible. Buy a high-quality, shed-resistant woven roller cover (3/8" nap for smooth walls, 1/2" nap for light texture) and a premium angled sash brush for cutting in corners.

By accurately estimating your materials and investing in quality paint and tools, you can achieve professional-level results that will transform your home and last for years to come.