How Much Area Will a Gallon of Paint Cover?

Last summer I painted a 1962 single-story in Tacoma. Cedar siding. Owner picked a deep navy over a chalky beige that had been there 30 years. I bought 12 gallons. Used 11. The chalk soaked the first coat like a sponge.

That job is the reason I never quote paint coverage from a can label without thinking it through first. The number printed on the bucket assumes a perfect world. Drywall is not a perfect world. Cedar shingles definitely are not.

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Quick Answer

A gallon of paint covers 300 to 400 square feet in one coat on smooth, primed drywall. That’s the standard manufacturer number from Sherwin-Williams, Benjamin Moore, and Behr. In the field, plan on 350 sq ft per gallon for interior walls and 250 to 300 sq ft per gallon for textured, porous, or rough surfaces. Most projects need two coats, which cuts your real-world coverage in half.

Coverage by Surface Type

The can says 350-400. Reality says it depends. Here’s what I actually get on different surfaces:

Surface	Coverage Per Gallon (1 Coat)	Notes
Smooth drywall, primed	350 - 400 sq ft	Best case, repaint over same color
New drywall, no primer	200 - 250 sq ft	Drinks paint, prime first
Textured drywall (orange peel, knockdown)	275 - 325 sq ft	Texture adds surface area
Wood trim, primed	300 - 350 sq ft	Most projects need 2 coats
Stucco	150 - 200 sq ft	Porous, deep texture
Brick (interior)	100 - 150 sq ft	Fills mortar joints, soaks paint
Cedar or rough siding	175 - 225 sq ft	Add 25% for first coat over weathered wood
Smooth fiber cement	250 - 300 sq ft	Primed factory finish
Concrete block	150 - 200 sq ft	First coat goes deep into the pores
Cabinet doors and boxes	250 - 300 sq ft	Spray finish, multiple thin coats

Source: manufacturer spec sheets (Sherwin-Williams ProClassic, Benjamin Moore Regal Select) cross-checked against 20+ years of field data on PNW residential repaints.

What Actually Eats Your Paint

Five things blow up coverage estimates. I’ve watched all five hit the same job at once.

• Porosity. New drywall, fresh joint compound, weathered wood, and concrete all soak paint. Prime first or budget 30-40% more material.
• Texture. Knockdown drywall has more surface area than smooth. Cedar shingles have way more. Stucco even more. The flatter the surface, the further your paint goes.
• Color change. Going from white to navy? Plan on three coats minimum, or a tinted primer plus two finish coats. Going from navy to white? Same problem in reverse.
• Sheen. Flat finishes hide better and cover faster. Semi-gloss and gloss show every roller mark and need more coats to look right.
• Application method. Brush and roll lays down thicker than spray. Spray covers more square footage per gallon, but a chunk of it ends up in the air or on your tarps. Net coverage is roughly the same.

Worked Example 1: 12 x 12 Bedroom Repaint

Standard PNW master bedroom, 8-foot ceilings, walls only, repainting the same color family.

• Wall area: Perimeter 48 ft x 8 ft = 384 sq ft
• Less doors and windows: subtract ~40 sq ft = 344 sq ft net
• Coats: 2 (standard repaint, no primer needed)
• Total paint area: 344 x 2 = 688 sq ft
• Coverage assumption: 350 sq ft per gallon
• Paint needed: 688 / 350 = 2 gallons

Material cost at standard quality: 2 gallons x $40 = $80.

A homeowner doing this themselves over a weekend will spend about $130 with rollers, brushes, plastic, and tape. A pro charges $400-$700 for the same room turnkey.

Worked Example 2: 30 x 40 Garage Interior, First Paint

New construction garage, primed drywall, owner wants a clean white finish before move-in.

• Wall area: Perimeter 140 ft x 10 ft = 1,400 sq ft
• Ceiling area: 30 x 40 = 1,200 sq ft
• Less garage door, man door, windows: subtract ~250 sq ft
• Net paint area: 2,350 sq ft
• Coats: 2 (primed but new, walls and ceiling)
• Total paint area: 4,700 sq ft
• Coverage assumption: 325 sq ft per gallon (drywall texture, cooler garage temps)
• Paint needed: 4,700 / 325 = 15 gallons, round to 15 gallons (3 five-gallon buckets)

Material cost: 3 x five-gallon buckets at $160 each = $480. Add another $40 for primer touchups, brushes, roller covers, and you’re around $525 in materials.

How to Calculate Paint for Your Project (5 Steps)

The math is the same whether you’re doing one wall or a whole exterior. Follow these in order.

1. Measure each wall. Length x height. Add them all up. Don’t forget hallways, soffits, and trim returns.
2. Subtract openings. Doors are about 21 sq ft each. Windows vary, average 15 sq ft for a standard double-hung. Garage door is the size of the garage door. Don’t subtract small punches like outlets.
3. Multiply by number of coats. Two for most jobs. Three if you’re going light over dark or dark over light without primer.
4. Divide by coverage rate. Use the table above based on your actual surface. When in doubt, use 350 sq ft for interior smooth walls and 250 for exterior or textured.
5. Round up and add 10%. Always. You’ll need it for cut-in touchups, that one corner you missed, or matching color six months later when you scuff a wall.

For a faster version of all five steps in one shot, use our paint calculator or read the full breakdown in how much paint do I need.

Common Mistakes I See

These are the ones that cost real money on real jobs.

• Trusting the can label literally. The 400 sq ft number assumes brand-new, primed, smooth drywall in a 70-degree room with experienced applicators. Reality is usually 300-350.
• Skipping primer on bare wood or new drywall. You’ll spend more on extra finish coats than you saved on the primer. Primer is cheap insurance.
• Buying enough for one coat. Two coats is the standard. Selling a homeowner on a one-coat job and then having to come back for touchups burns trust and time.
• Mixing partial gallons from different batches. Even the same color can shift between lots. Always box your paint (mix all gallons together in a 5-gallon bucket) before you start a wall.
• Estimating coverage on cedar or stucco the same as drywall. I learned this the hard way on the Tacoma navy job. Cedar drinks paint. Stucco drinks more. Always cut your coverage estimate by 30-40% on rough exterior surfaces.

Paint Quality and Coverage

Here’s the trade-off. A $25 economy gallon and a $65 premium gallon technically claim the same coverage on the label (350-400 sq ft). The difference is hide and durability.

Premium paint covers in fewer coats over a color change. Standard does fine over same-color repaints. Economy is for closets, rentals, and garages where you can live with two coats and the occasional touchup.

For a kitchen wall that gets cleaned weekly, I won’t put cheap paint on it. The coating burnishes (gets shiny where you wipe) within a year. For a guest bedroom that gets repainted every 5 years anyway, economy is fine.

Regional Cost Note

Paint material prices are roughly the same nationwide. Labor varies a lot. Painter wages run $48,660 median per BLS 47-2141 (May 2024), but in a high-cost metro you’ll pay 30-40% more per square foot than in a lower-cost market. Always check local rates if you’re estimating a labor-included paint job. For a deeper breakdown, see interior painting cost per square foot.

FAQ

How many gallons of paint do I need for a 12x12 room? Two gallons covers a standard 12x12 bedroom with 8-foot ceilings, painting walls only with two coats over the same color family. If you’re painting the ceiling too, add one more gallon. Going from light to dark or dark to light? Add a gallon for primer.

Will one gallon of paint cover one coat on 400 square feet? On smooth, primed drywall in a controlled environment, yes. In the field on real jobsites with normal texture and average application, plan on 300-350 sq ft per gallon for one coat. The 400 number is a best-case scenario.

Why does new drywall need so much more paint? Unsealed drywall and joint compound are porous. The first coat soaks in instead of building a film on top. That’s why a primer or PVA sealer is mandatory on new drywall. It saves you a full extra coat of finish paint.

Does paint coverage change for ceilings vs walls? Coverage is the same per square foot, but ceilings often need a thicker application to look uniform under direct light. Most pros use a dedicated ceiling paint (flat, high-hide) and plan on 300 sq ft per gallon to be safe.

How much exterior paint do I need for a 2,000 sq ft house? Average two-story 2,000 sq ft home has roughly 2,400 sq ft of paintable wall area. Two coats at 250 sq ft per gallon (typical for siding) means 19-20 gallons of body paint. Add 1-2 gallons for trim and 1 gallon for accent doors. Run the numbers through our exterior paint calculator to dial it in to your exact house.

Can I mix leftover paint to save money? Only if it’s the exact same product, color, and sheen. Mixing flat with eggshell or two slightly different whites will give you patches you can see in raked light. Box matching gallons (combine in a 5-gallon bucket) is fine and recommended for big jobs.

Stop Guessing on Paint Quantities

Twenty years on PNW jobsites taught me that paint estimates fail in the same three places: bad measurements, optimistic coverage rates, and forgetting the second coat. Get those three right and you’ll be within 10% on every project.

Contractors using EstimationPro report estimates that take 2 hours by hand drop to under 5 minutes, with paint quantities, labor, and material markup pulled in automatically. Try EstimationPro free and let it build the proposal, send it to your client, and run the automated follow-up sequence so you actually win the bid instead of losing it to a contractor who quoted faster.