How Much Paint for a 12×12 Room? 7 Factors To Consider

A room prepped to be painted with plastic sheeting, a ladder, and paint roller.

When painting a 12×12 room, choosing a paint color and a paint brand is only half the battle. You still have to prep the room, clean the walls, test the paint color, and decide how much paint you’ll actually need. 

How much paint is needed for a 12×12 room? A 12×12 room needs about 1.5 gallons of paint to cover all four walls plus the ceiling with some leftover for accents, touch-ups, and moldings. Factors that may impact the actual amount needed include the height of the walls, number of windows and doors, paint quality, and number of coats needed.

Every room is different, however, which is why we’ve made this comprehensive guide on how much paint you actually need for your room. 

Read on to learn how to estimate how much paint you need according to the room’s wall height, the quality of the paint, and the condition of the walls among others. 

Let’s dive right in! 

How Much Paint for a 12×12 Room – Factors To Consider

There are multiple factors to consider when estimating how much paint a 12×12 room needs, including the room’s wall height, the number of windows and doors, the condition of the walls, and the number of coats you’re planning to apply. 

In general, though, a standard 12×12 room (with eight-foot-high walls) would more or less require around 1.5 gallons of paint.

Here are some factors that may affect this figure: 

Wall Height

The first thing you need to consider when buying paint is the length and height of the room. Doing so will help you figure out the room’s total square footage. 

You can find the area of each wall by multiplying its width by its height. In the case of a 12×12 room, the square footage is 144. 

Will Ceilings Be Painted or Not

If you’re planning to paint the ceilings, you’ll naturally need more paint. 

To properly calculate this, you need to measure the highest point of the ceiling alongside the length and height of the wall. 

Note that sloped and textured/popcorn ceilings require more paint than flat, non-textured ceilings. 

For sloped ceilings, calculate the triangular wall space by multiplying the base of the triangle by its height and then dividing that number by two.

Otherwise, you’ll simply need to measure the length and width of the floor area and multiply them together to find the ceiling area.  

Number of Windows and Doors

The doors require additional paint due to the surface area they cover. Window area, aside from the framing, will not require paint.

Measure the height and width of the door and/or window, then multiply them together to get the estimated surface area. Repeat for each window and door. 

If the doors will be painted, add their area to your calculations. Subtract the window dimension from the wall area as you will not be painting the window glass.

Quality of Paint

High-quality paint with good pigmentation offers more coverage and thus reduces the need to apply more than one or two coats at a time. 

If you’re using low-quality paint, you’ll likely need to buy double and sometimes even triple the amount of high-quality paint to fully cover a room. 

Condition of Walls

The existing conditions of your walls will also affect how much paint the room needs.

If your walls are cracked/damaged or have a lot of structural elements, you’ll need around 20% more paint than a regular wall. 

Thickness Applied

A single coat of paint has a thickness of 0.1 to 0.2 millimeters. The thicker the application, the more paint you’ll need.

Generally, two to three coats are enough, but if you apply very thin coats, more might be needed. 

Number of Coats Required

For interior walls, you need only two coats of paint: the first coat and a finish coat.

There are some cases that require you to use more than two coats though, like when you’re painting dark colors. If the room needs two coats, a gallon of paint is enough to cover 200 square feet. 

How Much Does a Gallon of Paint Cover?

A single gallon of high-quality paint covers around 350 to 400 square feet. So for a 12×12 room, you need approximately 1.5 gallons of paint for two coats including the ceiling. 

A woman using a roller to paint a wall purple.

Do You Have To Primer a Wall Before Painting?

You don’t always need to prime your walls before painting.

In some cases, it can be omitted entirely—especially if the walls you’re painting are smooth, clean, and covered with the same type of paint as the new one. 

However, if the walls have some imperfections or have never been painted before, priming the walls is crucial to avoid cracking, fading, and long-term damage. 

Do I Need to Use Primer on Already Painted Walls?

In most cases, no, you don’t need to use primer on already painted walls. 

Just make sure to prep the walls beforehand: wash the walls to remove grime, grease, and stains, fill in holes or cracks with fillers, sand uneven textures, etc.  

What Happens if You Don’t Use Primer?

If you’re painting walls without priming them first, the color will appear light and washed out as a result of the pigment soaking into the drywall. This forces you to apply more coats than necessary. 

The paint might not properly adhere to the walls either, especially if you’re using latex paint on a wall that was previously covered in oil-based paint. 

How Many Coats of Primer Do I Need?

Typically, you need two to three coats of primer to ensure a proper bond between the wall and the new paint.  

How Long Does Primer Take To Dry?

Primer drying time really depends on the primer type, humidity, room temperature, and the surface you’re painting. 

Most primers dry in one to two hours, but you should always wait at least three hours before applying a layer of paint. 

How Many Coats of Paint on Wall?

A minimum of two coats is required when painting walls. With two coats, the paint won’t peel, crack, or fade as quickly.

The paint will last longer, and although it’ll require you to buy double the amount of paint, it’ll cost you less money in the long run for wall repairs and paint replacement. 

Is One Coat of Paint Enough?

If the paint is made with heavy, thick acrylic-latex, one coat is enough as thick acrylic-latex equals two coats of paint. 

Otherwise, a single coat of paint won’t suffice as it won’t give you complete coverage.

If you’ve primed your walls or painted the walls with the same color they had before, you can get away with a single coat. 

How Many Coats of Paint Is Too Much?

“Too much” is quite subjective as it depends on the quality and the color of the paint. Some paints become “too much” after only three coats and others after five or six. 

In general, you want no more than three coats if you’re using high-quality paint. 

Related Questions: 

What To Do With Leftover Paint?

When buying paint, it’s always safer to buy extra so you don’t run out halfway. However, this also leaves you with a ton of leftover paint hanging out in your shed or garage.

Here are some ideas to use leftover paint: 

  • Make an accent wall or door 
  • Touch-up old furniture 
  • Add color to kitchen trims, cabinets, and accessories 
  • Paint a portrait or a mural
  • Paint the frame of a mirror 
  • Paint the fireplace 

How To Remove Dried Paint Drips From Wall?

To remove dried paint drips from walls, gently scrape the drips with a razor or chisel. Then, smooth out the surrounding surface and touch up the spot with leftover paint. 


The amount of paint you need to paint a 12×12 room depends on many factors, including the quality of the paint, the conditions of the wall, and the wall height among others.

Generally, 1.5 gallons is sufficient to cover all four walls plus the ceiling. 


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I'm a hobby enthusiast with a real love for painting miniatures. I also happen to run this site and write the majority of its content!