One gallon of interior paint covers approximately 350 to 400 square feet per single coat on smooth drywall. One gallon of exterior paint covers approximately 300 to 350 square feet per coat. One gallon of primer covers approximately 200 to 300 square feet per coat. These are industry-standard figures published by Sherwin-Williams, Benjamin Moore, and Lowe’s, and they apply to brush and roller application on surfaces in normal condition.
Since most painting projects require two coats, the practical coverage per gallon drops to 175 to 200 square feet for interior walls and 150 to 175 square feet for exterior surfaces. That means a typical bedroom needs about 2 gallons, and a full-home interior repaint on a 2,000 sq ft house needs roughly 10 to 15 gallons depending on the number of rooms, ceiling height, and whether trim and ceilings are included.
Paint Coverage by Type
Not all paint products cover the same area per gallon. Coverage depends on the paint formula, the percentage of solids in the product, and what surface it is designed for.
| Paint Type | Coverage Per Gallon (1 coat) | Coverage Per Gallon (2 coats) |
| Interior latex/acrylic (walls) | 350 to 400 sq ft | 175 to 200 sq ft |
| Exterior latex/acrylic | 300 to 350 sq ft | 150 to 175 sq ft |
| Interior primer | 200 to 300 sq ft | N/A (1 coat typical) |
| Exterior primer | 200 to 250 sq ft | N/A (1 coat typical) |
| Ceiling paint (flat) | 350 to 400 sq ft | 175 to 200 sq ft |
| Trim and door enamel (semi-gloss) | 350 to 400 sq ft | 175 to 200 sq ft |
| Stain-blocking primer | 200 to 300 sq ft | N/A (1 coat typical) |
| Cabinet paint | 300 to 350 sq ft | 150 to 175 sq ft |
Premium paints from brands like Sherwin-Williams and Benjamin Moore tend to cover on the higher end of these ranges because they contain a higher percentage of solids (pigment and resin) and less water filler. Builder-grade and budget paints often fall on the lower end, sometimes requiring a third coat to achieve full coverage, which negates any material cost savings.
How Many Gallons Do You Need by Room Size?
Here is a quick reference chart based on standard 8-foot ceilings with window and door deductions already factored in:
| Room Size | Paintable Wall Area (approx.) | Gallons Needed (2 coats) |
| 8 x 10 ft | 260 sq ft | 1.5 gallons |
| 10 x 10 ft | 290 sq ft | 1.5 to 2 gallons |
| 10 x 12 ft | 320 sq ft | 2 gallons |
| 12 x 12 ft | 350 sq ft | 2 gallons |
| 12 x 14 ft | 380 sq ft | 2 gallons |
| 14 x 16 ft | 440 sq ft | 2.5 to 3 gallons |
| 16 x 20 ft | 530 sq ft | 3 gallons |
| Full home (1,500 sq ft) | 3,500 to 4,500 sq ft of wall | 10 to 12 gallons |
| Full home (2,500 sq ft) | 5,500 to 7,000 sq ft of wall | 15 to 18 gallons |
These estimates cover walls only. Add roughly 1 gallon per 400 sq ft of ceiling if you are painting ceilings as well. Trim, baseboards, and doors are typically calculated separately at about 1 quart per 100 square feet of trim surface.
How to Calculate Paint Coverage for Any Room
Use this formula to figure out exactly how many gallons you need:
Step 1: Measure the total perimeter of the room (add all wall lengths together).
Step 2: Multiply the perimeter by the ceiling height to get total wall area.
Step 3: Subtract 20 sq ft for each standard window and 20 sq ft for each standard door.
Step 4: Divide the remaining square footage by 400 (for interior paint) to get gallons per coat.
Step 5: Multiply by 2 for two coats.
Worked Example
A room that is 12 ft x 14 ft with 8 ft ceilings, two windows, and one door:
- Perimeter: 12 + 12 + 14 + 14 = 52 ft
- Total wall area: 52 x 8 = 416 sq ft
- Subtract openings: 416 – (2 x 20) – (1 x 20) = 356 sq ft
- Gallons per coat: 356 / 400 = 0.89 gallons
- Gallons for 2 coats: 0.89 x 2 = 1.78 gallons
- Buy 2 gallons. Always round up.
What Affects Paint Coverage?
The 350 to 400 sq ft figure is a baseline, not a guarantee. Several factors increase or decrease how far a gallon goes.
Surface Texture
Smooth drywall gives you maximum coverage. Textured walls like orange peel, knockdown, or heavy stipple have more surface area per square foot and absorb more paint, reducing coverage to 250 to 350 sq ft per gallon depending on the depth of the texture.
Surface Porosity
New, unpainted drywall absorbs significantly more paint than previously painted walls. That is why primer (200 to 300 sq ft per gallon) is applied first on bare surfaces. The primer seals the porous drywall so the topcoat goes on evenly and does not soak in unevenly, which causes blotchy color and requires additional coats.
Paint Color
Covering a dark wall with a light color or vice versa usually requires an extra coat. A tinted primer that matches the general tone of your new color reduces the number of topcoats needed.
Paint Quality
Premium paints contain 40% to 50% solids (pigment and binder), while budget paints may contain only 25% to 35%. Higher solids means better coverage per coat, better hide, and fewer coats needed to achieve full opacity. On a full-room project, premium paint often uses fewer gallons overall despite the higher price per gallon.
Application Method
| Application Method | Transfer Efficiency | Effective Coverage Per Gallon |
| Brush and roller (hand applied) | ~100% | 350 to 400 sq ft |
| HVLP spray gun | ~65% | 225 to 260 sq ft |
| Airless sprayer | 35% to 40% | 125 to 160 sq ft |
Brush and roller application is the most efficient in terms of material use because almost all the paint ends up on the wall. Spraying is faster but wastes 35% to 65% of the paint as overspray. Professional painters factor this waste into their material estimates when using spray equipment.
Number of Coats
Almost every project requires two coats for proper coverage and a uniform finish. A single coat may look adequate while wet but often shows thin spots, roller marks, and color inconsistency once it dries. Two thin coats always outperform one thick coat in both appearance and durability.
Temperature and Humidity
Paint applied in extremely hot or humid conditions can dry too fast and not level properly, which reduces the effective coverage. In Atlanta’s climate, where summer humidity regularly exceeds 70%, exterior painting is best scheduled during spring and fall when conditions allow proper curing.
How Many Gallons for a 5-Gallon Bucket?
A 5-gallon bucket of interior paint covers approximately 1,750 to 2,000 square feet per coat (5 x 350 to 400). With two coats, that is roughly 875 to 1,000 square feet of actual wall coverage, enough for 2 to 3 average-sized rooms.
5-gallon buckets are cheaper per gallon than buying individual gallons and are the standard for whole-room or multi-room projects. They also reduce the risk of color variation between batches, since all 5 gallons are mixed together.
Interior vs. Exterior Paint Coverage
| Factor | Interior Paint | Exterior Paint |
| Coverage per gallon (1 coat) | 350 to 400 sq ft | 300 to 350 sq ft |
| Coverage per gallon (2 coats) | 175 to 200 sq ft | 150 to 175 sq ft |
| Formulation | Thinner, optimized for smooth drywall | Thicker, more resin for weather resistance |
| Typical surfaces | Smooth drywall, plaster | Wood grain, fiber cement, stucco, brick |
| Why coverage differs | Smooth surfaces absorb less paint per sq ft | Rougher textures create more surface area and absorb more paint |
For exterior projects in Atlanta, professional painters estimate material based on paintable exterior surface area, not the home’s floor plan square footage. A 2,000 sq ft home might have 2,800 to 3,500 sq ft of paintable exterior surface depending on the number of stories, architectural detail, and siding type.
Primer Coverage vs. Paint Coverage
| Factor | Primer | Paint |
| Coverage per gallon | 200 to 300 sq ft | 350 to 400 sq ft |
| Purpose | Seal, bond, and block stains | Provide color and finish |
| Coats needed | 1 coat standard | 2 coats standard |
| Required on | New drywall, drywall repairs, bare wood, stains, drastic color changes | All paintable surfaces after primer |
| What happens without it | Topcoat absorbs unevenly, needs 3 to 4 coats for full opacity | N/A |
| Cost impact | 1 gallon of primer + 2 coats of paint uses less total material than 3 to 4 coats of paint alone | Skipping primer wastes more paint than it saves |
The extra gallon of primer is not an added expense. It is a material saver that reduces the total number of paint coats needed and delivers a more uniform, longer-lasting finish.
Frequently Asked Questions
How many square feet does one gallon of interior paint cover?
One gallon of interior latex or acrylic paint covers approximately 350 to 400 square feet per single coat on smooth drywall. With two coats, one gallon covers about 175 to 200 square feet of finished wall area.
How much paint do I need for a 12×12 room?
A 12×12 room with 8-foot ceilings has roughly 350 square feet of paintable wall area after deducting windows and a door. You need about 2 gallons for two coats of wall paint, plus 1 quart if you are painting the ceiling separately.
How many gallons of paint for 1,000 square feet of wall?
Approximately 2.5 to 3 gallons for one coat, or 5 to 6 gallons for two coats, assuming smooth drywall and standard interior latex paint at 400 sq ft per gallon.
Does primer cover the same area as paint?
No. Primer covers approximately 200 to 300 square feet per gallon, about 25% to 40% less than paint. Primer is formulated to seal and bond rather than cover, so it goes on thicker per square foot.
Does textured walls use more paint?
Yes. Textured surfaces like orange peel, knockdown, and heavy stipple can reduce coverage to 250 to 350 square feet per gallon because the texture creates more surface area and absorbs more paint into the peaks and valleys.
How much paint does a 5-gallon bucket cover?
A 5-gallon bucket of interior paint covers approximately 1,750 to 2,000 square feet per coat, or 875 to 1,000 square feet with two coats. That is enough for 2 to 3 average-sized rooms.
Does spraying use more paint than rolling?
Yes. Spraying wastes 35% to 65% of paint as overspray depending on the equipment type. Brush and roller application is nearly 100% efficient. A project that takes 2 gallons by roller may need 3 to 4 gallons by airless sprayer.
Should I always buy extra paint?
Yes. Always round up your calculation and buy at least one extra quart. Running out of a custom-mixed color mid-project means a second trip and a potential color mismatch between batches. Most paint stores accept returns on unopened gallons.
Let the Pros Handle the Math
Estimating paint coverage, buying the right amount, and making sure every coat goes on evenly takes experience. G&G Professional Painting handles interior, exterior, cabinet, and commercial painting across the Atlanta metro using premium Sherwin-Williams and Benjamin Moore coatings, and we never run short on material.
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