For a standard, smooth, and primed interior wall, a gallon of paint covers approximately 350 to 400 square feet per coat. This is the number you will see on the label.
However, experienced painters know that real-world factors like wall texture, paint quality, and your application method can easily reduce this coverage by 20% or more, requiring you to buy extra gallons.
Why Is Accurate Paint Coverage Important?
Running out of paint halfway through a wall creates a nightmare. The new batch may not match perfectly, even if it’s the same color code. I’ve seen homeowners waste entire weekends and hundreds of dollars trying to fix color variations.
Buying too much paint isn’t smart either. A gallon costs $30 to $80 depending on quality. That extra gallon sitting in your garage for years? Wasted money. Last month, a client in La Jolla calculated their paint needs perfectly and saved $240 by avoiding overbuying for their 2,000 square foot home.
Here’s what accurate estimates give you:
- Consistent color across all walls: Paint batches vary slightly. Buying the right amount from one batch keeps color uniform.
- Better project planning: You’ll know your total costs upfront. No surprise trips to the store or budget overruns.
- Less waste: Leftover paint often goes bad before you need it again. Proper estimates mean less disposal hassle.
I’ve worked with contractors who estimate poorly. They either run short and delay projects by days, or they overbuy and eat the cost. A 3,000 square foot house exterior can waste $500 in paint if you don’t calculate correctly.
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.
Let’s get specific with real coverage rates I’ve tracked across hundreds of projects.
- Standard wall paint: 375 to 425 square feet per gallon on smooth, primed surfaces. This works for most interior walls in good condition.
- Primer: Only 225 to 275 square feet per gallon. Primer soaks into surfaces more, so you need more of it.
- Ceiling paint: 350 to 400 square feet per gallon. Ceilings often need textured coverage, which uses more paint.
- Trim paint: 375 to 425 square feet per gallon, but trim work involves more cutting and detail, so actual coverage feels lower.
These numbers assume two coats. One gallon gives you about 200 square feet of finished coverage when you apply the recommended two coats.
Real Project Example: Standard Bedroom
Last week, we painted a 12×14 foot bedroom in Carlsbad. Here’s the exact breakdown:
- Wall height: 9 feet
- Total wall area: (12+14+12+14) x 9 = 468 square feet
- Minus door and window (40 sq ft): 428 square feet
- Two coats needed: 856 total square feet
- Paint used: 2.5 gallons for complete coverage
The homeowner initially bought only 2 gallons. We ran short and had to pause the project. The lesson? Always round up.
Surface Type Changes Everything
- Smooth drywall: Gets the best coverage at 400 square feet per gallon. The paint glides on evenly.
- Textured walls: Drop to 300-320 square feet per gallon. The bumps and valleys create more surface area. In San Diego, many homes have textured ceilings. Plan for 20% more paint.
- Stucco exterior: Only 250-300 square feet per gallon. Stucco drinks paint. A typical San Diego home with 1,500 square feet of exterior stucco needs 12-15 gallons for two coats.
- Bare drywall: Extremely porous. Apply two coats of primer first (covers 225-275 sq ft per gallon), then your paint. Without primer, bare drywall can soak up three coats of paint.
- Brick: Similar to stucco at 250-300 square feet per gallon. All those grout lines add up.
Paint Quality Makes a Difference
I’ve tested every major brand. Here’s what I’ve found:
- Sherwin-Williams Duration: Covers about 400 square feet per gallon. Excellent hiding power. One of my favorites for dramatic color changes.
- Benjamin Moore Regal Select: Similar coverage at 400 square feet. Great for smooth finishes.
- Behr Premium Plus: Covers 350-400 square feet. Good budget option, though you might need that second coat more often.
- Budget brands: Often cover only 300-350 square feet. You’ll use more paint, which cancels out the savings. I stopped using cheap paint years ago after too many callbacks for thin coverage.
Factors That Affect Paint Coverage
While the average is useful, true expertise comes from understanding the variables that can lower your expected coverage. This prevents running out of paint mid-job.
1. Surface Texture and Porosity
Porous surfaces soak up paint like a sponge. Fresh drywall, raw wood, and masonry are highly absorbent. Textured walls, like popcorn ceilings or heavy stucco, have more surface to cover than a flat wall. For these rough surfaces, you must reduce your coverage expectation by 20% to 30%.
2. Paint Quality and Composition
Paint quality is one of the biggest factors in coverage, or “hide.”
- High-quality paints use better pigmentation and have a higher volume of solids, meaning they leave more color on the wall with one pass.
- Cheaper, lower-quality paints are thinner and require more coats of paint to achieve full color.
3. Impact of Sheen (Finish)
The sheen of the paint affects its thickness and how it spreads:
- Flat/Matte Finishes: These are usually thicker and tend to offer the best initial paint coverage, especially for hiding imperfections.
- Eggshell/Satin Finishes: These are slightly thinner and offer moderate coverage, popular for living rooms and bedrooms.
- Semi-Gloss/Gloss Finishes: These are often the thinnest, offering the least coverage per gallon, but they are used for durable areas like trim, doors, and cabinets.
4. Primer Type Differentiation
It is not enough to just use a primer. Using the right primer for the job is a professional move that saves paint and time.
Primer Type | Best Use Case | Why It Saves You Paint |
High-Build Primer | Damaged, patched, or heavily textured drywall. | It thickens to fill small imperfections, creating a smooth surface that reduces the amount of final paint needed. |
Stain-Blocking Primer | Covering water stains, smoke damage, or heavy permanent marker. | It locks in the stain completely, eliminating the need for 3-4 extra topcoats of paint. |
Bonding Primer | Hard-to-paint surfaces like glass, tile, or glossy laminate. | It creates a durable anchor, allowing your topcoat to stick without peeling off, ensuring no coverage is lost to poor adhesion. |
How to Estimate Paint Quantity Accurately
Here’s the exact method I use for every estimate. No guessing, just simple math.
Step 1: Measure your walls. Multiply width times height for each wall. A 12-foot wide by 9-foot tall wall is 108 square feet. Add all walls together for total square footage.
Step 2: Subtract what you won’t paint. Measure doors (usually 20 sq ft each) and windows (15-25 sq ft each). Subtract these from your total.
Step 3: Account for multiple coats. Most projects need two coats. Multiply your paintable area by two.
Step 4: Divide by coverage rate. Use 350 square feet per gallon as a conservative estimate. This builds in a safety margin.
Step 5: Round up and add extra. Always round to the next full gallon. Then add 10% for touch-ups and mistakes.
Real Math: Living Room Example
A client in Point Loma wanted their living room painted. Here’s how I calculated:
- Four walls: 15×9, 15×9, 20×9, 20×9 = 630 square feet
- Two windows (40 sq ft) and one door (20 sq ft) = 60 square feet
- Paintable area: 630 – 60 = 570 square feet
- Two coats: 570 x 2 = 1,140 square feet
- Gallons needed: 1,140 ÷ 350 = 3.26 gallons
- Round up: 4 gallons
We used 3.5 gallons. The extra half-gallon went to touch-ups six months later when they scuffed a corner moving furniture.
Use a Paint Calculator for Speed
Online paint calculators do this math instantly. Sherwin-Williams and Benjamin Moore both offer free tools. I still double-check by hand for large projects, but calculators work great for simple rooms.
The paint calculator gives you a starting point. Then adjust based on surface texture and paint quality.
Tips to Maximize Paint Efficiency
After painting hundreds of homes, I’ve learned tricks that stretch every gallon further.
- Prime first, always: A tinted primer costs $25-35 per gallon. It saves you from applying three coats of expensive paint. On a recent El Cajon project, primer saved us 2 gallons of paint worth $140.
- Choose the right tools: I use a 9-inch roller with a 3/8-inch nap for smooth walls and a 1/2-inch nap for textured surfaces. Cheap rollers soak up paint and splatter. Quality rollers (around $8-12) apply paint evenly and use 15-20% less.
- Don’t overload your roller: Many DIYers dip too much paint. Roll off excess on the tray. This prevents drips and spreads paint more evenly.
- Control your environment: Paint at 50-85°F with low humidity. Hot, dry conditions make paint dry too fast, forcing you to apply more coats. In San Diego summers, I paint early mornings or late afternoons.
- Back-roll after spraying: If you spray paint, back-roll immediately. This works the paint into the surface and improves coverage by 20%.
- Keep a wet edge: Don’t let paint dry between sections. Dried edges create lap marks that show through, requiring extra coats to hide.
- Buy all paint at once: Get everything from the same batch. Stores can’t guarantee perfect color matching between batches. I learned this the hard way on a Mission Valley condo project years ago.
Special Situations Need Extra Paint
- Dark to light color changes: Going from navy blue to white? You’ll need three coats minimum. Use a gray-tinted primer first. This saved a Chula Vista client from applying four coats of white.
- Old, unpainted walls: Homes built before 1990 often have walls that haven’t been painted in decades. These surfaces are thirsty. Plan for three coats or heavy-duty primer.
- Popcorn ceilings: These texture nightmares use 30% more paint than flat ceilings. A 200-square-foot popcorn ceiling needs almost 2 gallons for two coats instead of the normal 1.5 gallons.
Choosing the Right Paint for Your Project
Paint type changes both coverage and results. Here’s what works best for different situations.
- Flat paint: Best coverage at 400+ square feet per gallon. Hides imperfections well. Use on ceilings and low-traffic walls. The downside? It can’t be scrubbed clean.
- Eggshell/satin: Covers 375-400 square feet per gallon. My go-to for living rooms and bedrooms. It’s clean and looks great.
- Semi-gloss: Covers 350-375 square feet per gallon. Reflects light, so imperfections show more. Perfect for kitchens, bathrooms, and trim. Easy to wipe clean.
- High-gloss: Covers only 325-350 square feet per gallon. Very reflective. Use sparingly on doors and cabinets.
For most interior walls, I recommend satin finish. It balances coverage, durability, and appearance. In high-moisture areas like bathrooms, semi-gloss prevents mold better.
Paint + Primer Combinations
Many brands now sell paint with built-in primer. Do they work? Sometimes. On previously painted walls in good condition, they’re fine. But for bare drywall, dramatic color changes, or stained surfaces, separate primer works better.
I tested this on two identical rooms. One got separate primer and paint. The other got a paint-and-primer combo. The separate primer room looked better and used less total paint.
Why Quality Paint and Tools Matter
Cheap paint seems like a bargain until you apply it. Here’s what I’ve learned about paint cost per gallon versus actual value.
- Budget paint ($25-35/gallon): You’ll apply three coats for solid coverage. Total cost: 3 gallons x $30 = $90 plus extra labor.
- Premium paint ($50-80/gallon): Two coats give complete coverage. Total cost: 2 gallons x $65 = $130, but it looks better and lasts longer.
The math shows premium paint costs $40 more for the same room. But you save time, get better results, and the finish lasts 5-7 years instead of 3-4 years.
Real cost comparison: I painted two identical 300-square-foot rooms. One used budget paint, one used Sherwin-Williams Duration.
- Budget room: 3 gallons needed, 6 hours of work, faded after 3 years
- Premium room: 2 gallons needed, 4 hours of work, still looks fresh at 5 years
The premium paint saved 2 hours of labor (worth $80-100 for pros) and looked better throughout.
Don’t Skimp on Tools Either
A $3 roller falls apart and leaves fuzz in your paint. A $10 Purdy roller applies paint smoothly and lasts through multiple projects. Quality brushes don’t shed bristles into your finish.
I once watched a homeowner use dollar-store tools. They needed an extra gallon of paint just to fix drips and thin spots. Good tools pay for themselves in paint savings alone.
Common Coverage Mistakes That Waste Paint
- Mistake 1: Forgetting about two coats. Most people calculate for one coat only. Two coats are standard for professional results.
- Mistake 2: Not accounting for texture. Smooth wall math doesn’t work for stucco or popcorn ceilings. Add 20-30% more paint.
- Mistake 3: Measuring floor area instead of wall area. A 200-square-foot room has about 650 square feet of wall space (with 9-foot ceilings). Big difference.
- Mistake 4: Buying quarts instead of gallons. Quarts cover about 100 square feet but cost almost half as much as a gallon. For anything bigger than touch-ups, gallons save money.
- Mistake 5: Mixing old paint with new. That half-gallon from two years ago? It’s probably separated and won’t match. Start fresh.
How Much Does 5 Gallons of Paint Cover?
Five gallons covers about 1,750 to 2,125 square feet with one coat, or 875 to 1,060 square feet with two coats. This handles a large living room, master bedroom, and hallway in one purchase.
Buying five-gallon buckets saves money too. A 5-gallon bucket costs $150-250, while five individual gallons cost $175-300. You save $25-50 per bucket.
Conclusion: How Much Does a Gallon of Paint Cover?
The simple answer remains: a gallon of paint covers 350 to 400 square feet on a smooth, primed wall. The real answer for a successful project lies in understanding the complex variables texture, primer use, sheen, and the number of coats required. Only by accurately factoring in these details can you move past simple estimates to a perfect material list.
If you are tackling a complex exterior job or large-scale interior painting and want guaranteed accuracy, let the experts handle it. San Diego Custom Painting provides specialized interior painting and exterior painting services in San Diego that account for the unique climate and surface types of the area. We remove the guesswork, ensuring you get the perfect finish the first time.
Ready to start your project with confidence? Contact San Diego Custom Painting today for a free estimate!
FAQs
How many square feet does 1 gallon of paint cover with two coats?
One gallon covers 175-200 square feet with two coats on smooth walls. Textured surfaces reduce this to 150-175 square feet per gallon.
How do I calculate how much paint I need?
Measure wall width times height to get total square footage. Subtract windows and doors. Multiply by 2 for two coats. Divide by 350 to get gallons needed. Always round up.
Does primer coverage differ from paint?
Yes. Primer covers only 225-275 square feet per gallon because it’s designed to soak into surfaces. You’ll need more primer than paint for the same area.
Why did I run out of paint before finishing?
Common reasons include underestimating square footage, not accounting for two coats, painting textured surfaces, or using cheap paint with poor coverage. Always buy 10% extra.
Can I mix leftover paint with new paint?
Only if the leftover paint is the same brand, sheen, and color from within the past year. Old paint separates and won’t match new batches perfectly. When in doubt, start fresh.
How much does paint quality affect coverage?
Premium paint covers 15-20% more surface area than budget paint. A gallon of Sherwin-Williams Duration covers 400 square feet reliably, while budget brands often cover only 300-350 square feet.
Do I need more paint for dark colors?
Yes. Dark colors require 2-3 coats for solid coverage versus 2 coats for light colors. Use tinted primer to reduce the number of paint coats needed.
How long does leftover paint last?
Properly sealed paint lasts 2-3 years in a cool, dry place. Freeze-thaw cycles ruin paint. If it smells bad or has chunks, throw it out.
