How to choose interior paint and work out how much to buy

The right interior paint turns a tired room into a fresh space in a single weekend. You need to match the sheen to the room's daily traffic and buy the correct number of gallons for your square footage. Testing colors on the wall first helps you avoid a shade you regret.

Pick a sheen for each room

The finish on your interior paint determines how much light the wall reflects and how easily it wipes clean. Glossier finishes are durable and resist moisture. Flatter finishes hide dents and uneven drywall patches. Match the sheen to the room's purpose and traffic level.

Flat or matte paint absorbs light and provides a smooth and velvety look. This sheen hides minor wall imperfections. It is difficult to clean without taking some paint off the wall. Ceilings and low traffic bedrooms are the best places for flat paint.

Eggshell has a faint shine that mimics the surface of an egg, striking a good balance between hiding flaws and offering a washable surface. Living rooms and dining rooms look great in eggshell because these spaces see moderate daily use. Eggshell provides a warm, soft background for wall decor without casting harsh glare from your lamps. You can gently wipe smudges away with a damp cloth.

Satin reflects more light than eggshell and stands up to regular scrubbing, resisting moisture and mildew better than lower sheens. Kitchen walls face splashing grease, boiling water, and sticky hands, but satin paint holds up to a mild degreaser and a sponge. Bathrooms generate heavy steam that penetrates flat paint and causes peeling, while satin finishes resist moisture better. Busy hallways and kids' rooms also need a durable satin finish.

Semi-gloss and high-gloss paints reflect a lot of light and highlight every flaw on the surface beneath them. These shiny finishes dry to a hard shell that handles frequent cleaning and heavy wear. Baseboards, window frames, interior doors, and cabinets require semi-gloss or gloss paint. You might use semi-gloss to highlight wall trim against an eggshell wall.

What separates good paint from cheap paint

High quality interior paint costs more because it contains better ingredients. The liquid in a paint can is a mixture of pigments, binders, and solvents. Premium paint has a higher ratio of solid pigments and strong binders.

Cheap paint contains more solvent, which simply evaporates into the air. A bargain can might look thick in the bucket but leaves a thin layer of color behind. You often need extra coats of cheap paint to hide the old wall color. The final surface is more likely to fade and chalk over time.

Quality paint applies smoothly and spatters less off the roller. High volume solids provide thick coverage that hides the old color in fewer coats. The stronger binders create a tough film that resists scratches and scrubbing. Spending more on a good can saves you hours of rolling and brushing.

Test colors on the wall before committing

A small paper swatch under fluorescent store lights looks completely different on your living room wall. Natural light changes throughout the day and alters how you perceive color. A gray shade might look cool and blue in the morning light but turn warm and purple by the afternoon. Artificial room lighting also shifts the color at night.

Every interior paint color carries subtle undertones that only reveal themselves under specific conditions. A crisp white might hide a yellow tint that suddenly looks creamy next to a gray sofa. A neutral beige can pull green when sunlight reflects off the trees in your yard.

Buy a small sample pot of your chosen color or order a large peel and stick paint swatch. Paint a large piece of poster board and tape it to the wall. This trick stops you from living with messy painted squares on your drywall for weeks while you decide. Moving the board from a sunny wall to a dark corner shows you exactly how shadows deepen the hue.

Look at the color in the morning, at noon, and after dark. Turn on your lamps and overhead lights to see how the paint reacts. Compare the sample to your flooring, furniture, and curtains. Take your time deciding before you buy expensive gallons and start to paint an accent wall or a whole room.

Measure walls and work out gallons

Guessing the amount of paint you need usually leaves you short on Sunday afternoon or stuck with expensive leftover cans. You want to measure the room and calculate the total square footage of the walls. Grab a tape measure, a notepad, and a calculator.

Work out the wall area like this:

• Measure the length of every wall in the room with a tape measure.
• Add those lengths together to find the total perimeter.
• Multiply the perimeter by the ceiling height to get your gross square footage.
• Measure the doors and subtract their square footage.
• Measure the windows and subtract their square footage.

Subtracting the doors and windows from your gross square footage gives you the exact wall area. Sherwin-Williams says a gallon of paint typically covers about 350 to 400 square feet, and a quart covers 100 square feet. Divide your exact wall area by 350 to find out how many gallons one coat requires.

Interior walls often need two coats for a smooth and even finish. Multiply your one coat gallon total by two. A room with 400 square feet of wall space needs at least two gallons for a thorough two coat finish, and often a little more.

Conditions that require a coat of primer

Primer is a base layer that binds securely to raw surfaces and creates a uniform foundation for your topcoat. It stops porous materials from soaking up your expensive interior paint. Paint covers better and lasts much longer when it goes over the right primer. Primer also helps your topcoat cover evenly.

New drywall and fresh joint compound require a coat of drywall primer before you paint. Bare wood needs a wood primer to seal the grain and prevent tannins from bleeding through. You also need a heavy duty blocking primer to cover water stains, smoke damage, or dark marker drawings. Primer stops those stains from showing right through your new color.

Many older homes feature baseboards and doors painted with oil based gloss. Modern latex interior paint may not stick directly to an oil based surface. It peels off in long rubbery strips if you skip the prep work. You must apply a heavy bonding primer over the old oil paint before rolling on fresh latex color.

Dramatic color changes also call for primer. Painting white over a dark navy blue wall can take many coats of expensive paint. One coat of tinted primer covers the dark base and lets your light paint finish the job in fewer coats. Sherwin-Williams says a gallon of primer covers about 200 to 300 square feet.

Ventilate while you paint

Fresh paint releases fumes into the air as the solvents evaporate and the finish dries. These fumes contain volatile organic compounds that can can cause headaches and dizziness. The EPA says paints contain organic solvents and that many VOCs are consistently higher indoors, up to ten times, than outdoors.

Keeping the air moving protects your health and helps the paint dry faster. Open the windows in the room you are painting as wide as they go. Position a box fan in the window and point the blades outward to pull room air outside. If you point the fan inward, you just blow paint fumes deeper into your house.

Hardware stores sell zero VOC and low VOC interior paint formulas. These modern options often smell less intense than traditional latex or oil cans. However, they still contain various chemicals and solvents that need to escape the room during the curing process. You still need fresh air circulating through the space.

Leave the fans running and the windows open for hours after you finish painting. The EPA advises increasing ventilation when using products that emit VOCs and buying only as much as you will use right away. Do not sleep in a freshly painted bedroom until the heavy paint smell completely dissipates.

Check for lead paint in an older home

Scraping and sanding old paint creates hazardous dust if the underlying layers contain lead. Lead exposure is a serious health risk for adults and can cause developmental problems in young children. The EPA says homes built before 1978 are more likely to have lead based paint, and renovation that disturbs painted surfaces can create a hazard.

Chips and dust are most likely where painted surfaces rub together, such as window frames and doors. Look for alligatoring on the surface, which is a cracking pattern that resembles reptile skin. You cannot identify lead just by looking at a smooth wall.

You must test the paint before you sand a rough patch or scrape away peeling chips in an older home. The EPA recommends a certified lead inspector or risk assessor to test surfaces, and if you use a swab kit, follow its directions exactly.

If the old paint is in good condition, the safest approach is often to leave it alone. Intact paint is usually not a problem, and the EPA says to avoid disturbing it. You only run into trouble when the old paint is chipping, peeling, or turning to dust from friction on window tracks. If you find loose lead paint, do not remove it yourself and hire a lead safe certified contractor.