Starting a paint project means you need to know one key thing: how much does a gallon of paint cover? Getting this wrong costs you time and money. You might run short halfway through or waste cash on extra gallons you never open. Most people guess wrong and end up making extra store trips or storing unused paint for years.
Here’s what you need to know upfront. One gallon typically covers 350 to 400 square feet with a single coat. That’s roughly the size of a small bathroom or bedroom. But many factors change this number, and knowing them helps you buy the right amount every time.
Why Is Accurate Paint Coverage Important?
Buying the wrong amount of paint creates real problems. When you run short, you have to stop mid-project and rush to the store. Paint batches vary slightly in color, so matching becomes difficult. Your walls might show subtle differences between batches.
Overbuying wastes money too. Quality paint costs between $30 to $70 per gallon. Buying two extra gallons means $60 to $140 down the drain. Plus, storing paint takes up space and often leads to dried-out cans you eventually throw away.
Getting paint coverage right saves you from both headaches. You finish on schedule, maintain color consistency, and spend only what you need.
How Many Square Feet Does a Gallon of Paint Cover?
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The standard answer is 350 to 400 square feet per coat. But this changes based on several factors.
Paint Type Makes a Difference
Wall paint covers about 375 to 425 square feet per gallon. Ceiling paint typically covers 350 to 400 square feet because ceilings often need thicker application. Trim paint gives you similar coverage at 375 to 425 square feet. Primer is different; it only covers 225 to 275 square feet because it soaks into surfaces more.
Surface Texture Changes Everything
Smooth drywall gives you the best coverage. A gallon stretches to its full 400 square feet potential here. Textured walls need 20 to 30 percent more paint. Stucco, popcorn ceilings, and brick have more surface area to cover. For a 100 square foot textured wall, plan on enough paint for 120 to 130 square feet.
Fresh drywall soaks up paint like a sponge. The porous surface needs at least two coats of primer before your first paint coat. Skip this step and one gallon might only cover 200 square feet instead of 400.
Paint Quality Affects Coverage
Higher quality paint contains more pigment and solids. This means better coverage with fewer coats. Budget paint often requires three coats where premium paint needs only two. That $20 savings per gallon disappears when you need extra gallons.
Application Method Matters
Spraying paint typically uses 20 to 30 percent more than rolling. The spray mist creates overspray that doesn’t land on your wall. Rolling with a proper nap thickness gives you the best efficiency. Use a 3/8-inch nap roller for smooth walls and a 1/2-inch nap for textured surfaces.
Number of Coats Required
Most projects need two coats for professional results. This cuts your total square footage per gallon in half. If one gallon covers 400 square feet in one coat, plan on 200 square feet for two coats. Dark color changes need even more coats. Painting over black with white might take three or four coats.
How to Calculate How Much Paint to Buy
Follow these steps to get accurate numbers for your project.
Step 1: Measure Your Walls
Multiply the width times the height of each wall. A 12-foot wide by 8-foot tall wall gives you 96 square feet. Do this for every wall you plan to paint. Add all the numbers together for your total square footage.
Step 2: Subtract Non-Paintable Areas
Measure your windows and doors. A standard door is about 20 square feet. A typical window ranges from 15 to 25 square feet. Subtract these from your total wall square footage. This gives you your actual paintable surface area.
Step 3: Calculate for Multiple Coats
Take your paintable surface area and multiply by the number of coats needed. Two coats means doubling your number. A room with 400 square feet of wall space needs paint for 800 square feet total.
Step 4: Account for Surface Type
Add 20 to 30 percent if you have textured walls. Subtract nothing for smooth, previously painted walls in good condition. Add 10 percent for fresh drywall even after priming.
Step 5: Divide by Coverage Rate
Use 350 square feet as your baseline for safety. Divide your total square footage by 350. This tells you how many gallons you need. Always round up to the nearest gallon or quart.
Real Example: 12×12 Bedroom
A 12×12 room with 8-foot ceilings has four walls. Two walls are 12 feet by 8 feet (96 square feet each). Two walls are 12 feet by 8 feet (96 square feet each). Total wall area equals 384 square feet.
Subtract one door (20 square feet) and one window (20 square feet). You get 344 square feet of paintable surface. For two coats, multiply by two: 688 square feet total. Divide by 350: you need 1.97 gallons. Buy 2 gallons for this room.
Using a Paint Calculator
Many paint brands offer online calculators. These tools speed up the math. Enter your room dimensions, number of doors and windows, and coats needed. The calculator gives you instant results. Most recommend buying 10 percent extra for touch-ups.
Room-by-Room Paint Requirements
Here’s what you typically need for common spaces, assuming two coats on smooth walls.
Bathroom: 1 to 2 Gallons
Most bathrooms range from 50 to 100 square feet of wall space. One gallon usually handles a small bathroom. Larger bathrooms with separate shower areas need closer to 2 gallons.
Small Bedroom: 2 Gallons
A 10×10 or 10×12 bedroom typically needs 2 gallons. This covers approximately 300 to 400 square feet of wall space with two coats.
Large Bedroom or Living Room: 2 to 3 Gallons
A 12×15 or larger room requires 2 to 3 gallons. Open concept spaces might need 3 to 4 gallons depending on wall length.
Whole House Interior: 10 to 15 Gallons
A typical 2,000 square foot home needs about 12 gallons for all interior walls. This assumes 8-foot ceilings and two coats throughout.
Exterior Painting
Exterior coverage differs significantly. Wood siding typically needs 1 gallon per 300 to 400 square feet. Stucco and brick need 1 gallon per 200 to 300 square feet. A 1,500 square foot exterior might need 10 to 15 gallons total.
The cost to paint a 3000 sq ft house exterior ranges from $3,000 to $8,000 professionally. DIY paint costs alone run $400 to $800 for materials.
Special Situations That Change Coverage
Dramatic Color Changes
Painting from dark green to light beige takes extra coats. The dark color shows through light colors easily. Use a tinted primer that matches your final color. This reduces the number of finish coats needed from four to two.
Painting Over Wallpaper
Never paint directly over wallpaper. Remove it first. If you must paint over it, use an oil-based primer. This prevents the wallpaper paste from bubbling. Expect 30 to 40 percent less coverage because the textured surface soaks up more paint.
Wood Surfaces
Bare wood is very porous. Prime with two coats before painting. Even after priming, raw wood absorbs more paint than drywall. Reduce your coverage estimate by 15 to 20 percent.
Previously Unpainted Concrete
Concrete basement walls need special treatment. Use concrete primer first. Regular paint coverage drops to about 250 square feet per gallon on rough concrete.
Paint Cost Breakdown
Understanding paint cost per gallon helps you budget accurately.
Budget Paint: $20 to $30 Per Gallon
Covers 300 to 350 square feet per coat. Usually requires three coats for full coverage. Real cost per square foot: $0.17 to $0.27.
Mid-Grade Paint: $35 to $50 Per Gallon
Covers 350 to 400 square feet per coat. Typically needs two coats. Real cost per square foot: $0.18 to $0.25.
Premium Paint: $55 to $75 Per Gallon
Covers 400 to 450 square feet per coat. Often covered in two coats with better results. Real cost per square foot: $0.24 to $0.37.
Premium paint costs more upfront but often saves money overall. Better coverage means fewer gallons. Better durability means less frequent repainting.
Five Gallons of Paint Coverage
How many square feet does 5 gallons of paint cover? Multiply single gallon coverage by five. For smooth walls with quality paint, 5 gallons covers 1,750 to 2,000 square feet with one coat. With two coats, expect 875 to 1,000 square feet of coverage.
Common Painting Mistakes That Waste Paint
Using Cheap Rollers
Low-quality rollers shed fibers and don’t hold enough paint. You make more trips to the tray and apply uneven coats. This wastes paint and time. Invest in a quality 9-inch roller with the proper nap thickness.
Skipping Primer
Many people skip primers to save money. This backfires quickly. Unprimed surfaces need three or four paint coats instead of two. You end up buying more paint than primer would have cost.
Not Stirring Paint Properly
Paint settles in the can. The pigments sink to the bottom. Painting without stirring means thin, streaky coverage. Stir thoroughly for at least three minutes before starting.
Overloading the Roller
Too much paint on your roller causes drips and waste. It also creates uneven texture. Load your roller moderately and make smooth, overlapping passes.
Ignoring Surface Preparation
Dirty or glossy walls don’t hold paint well. Clean walls before painting. Sand glossy surfaces lightly. Proper prep ensures paint adheres correctly and covers evenly.
Tips to Maximize Your Paint Coverage
- Buy quality paint and tools. The extra cost pays off in better coverage and easier application.
- Use tinted primer when making major color changes. This reduces the number of finish coats needed.
- Work in ideal conditions. Paint between 50 and 85 degrees Fahrenheit. Avoid high humidity days. Extreme temperatures affect how paint spreads and dries.
- Apply thin, even coats. Two thin coats always beat one thick coat. Thin coats dry faster and look smoother.
- Calculate 10 percent extra for touch-ups. Paint batches vary slightly. Having extra from the same batch ensures perfect matches later.
- Store leftover paint properly. Seal the lid tightly and store in a temperature-controlled space. Label the can with the room and date. Properly stored paint lasts three to five years.
How Much Does a Gallon of Paint Cover Conclusion
One gallon of paint covers 350 to 400 square feet per coat on smooth walls. Textured surfaces, fresh drywall, and porous materials reduce this coverage by 20 to 30 percent. Most rooms need two coats, effectively cutting the coverage in half. Calculate your exact needs by measuring walls, subtracting openings, and accounting for surface type.
Quality paint costs more upfront but provides better coverage and durability. Budget paint seems cheaper but often requires extra gallons to achieve the same results. Investing in proper tools like quality rollers and using primer when needed saves paint and money overall.
For professional results without the hassle, San Diego Custom Painting offers expert interior and exterior painting services in San Diego. Our experienced team accurately estimates paint needs, uses premium materials, and delivers flawless finishes. We handle everything from surface preparation to final cleanup, ensuring your project stays on budget and schedule. Contact us today for a free estimate and let our professionals transform your space with precision and care.
FAQs
How many gallons of paint do I need for a 10×10 room?
A 10×10 room with 8-foot ceilings needs about 1.5 to 2 gallons for two coats. This accounts for approximately 320 square feet of wall space after subtracting a door and window.
Does paint sheen affect coverage?
Yes. Flat paint typically covers better than glossy paint. Flat finishes hide surface imperfections and often need fewer coats. Semi-gloss and high-gloss show every flaw and might require an extra coat for even coverage.
Can I return unused paint?
Most stores accept unopened paint returns within 30 to 90 days. Opened cans are rarely returnable. Custom-mixed colors are usually non-returnable. Check your store’s specific policy before purchasing.
How long does paint last in storage?
Properly sealed latex paint lasts three to five years in a temperature-controlled space. Oil-based paint can last up to 15 years. Opened cans last less time. If paint smells bad or has separated badly, discard it.
Should I paint walls or ceiling first?
Paint ceilings first. This prevents ceiling paint from dripping on freshly painted walls. Let the ceiling dry completely before starting the walls. Cut in edges last for the cleanest finish.
How much does a quart of paint cover?
A quart covers approximately 90 to 100 square feet per coat. Quarts work well for small touch-up jobs, painting trim, or accent walls. Buy quarts instead of gallons when you need less than half a gallon.
