Paint Coverage Per Gallon (Interior, Exterior, Trim) | Coverage Rates Chart

A reference guide showing how much area one gallon of paint covers for interior walls, exterior siding, trim, and doors — organized by paint type, surface texture, and number of coats.

Paint Coverage Per Gallon (Interior, Exterior, Trim)

One gallon of paint covers 350–400 square feet on smooth interior walls, 250–350 square feet on exterior surfaces, and 200–300 square feet on trim and doors. The exact number depends on surface texture, paint type, and whether the surface has been previously painted or primed. This is one of the guides on OnSiteCalculator, written to help you estimate accurately before you buy.

The coverage chart below shows rates for every common paint and surface combination. For a project-specific estimate that accounts for room size, doors, windows, coats, and waste, use the paint calculator.

Paint Coverage Rates Chart

These rates assume one coat on a properly prepared surface. Coverage is listed as a range because surface porosity, application method (roller vs brush vs sprayer), and paint quality all affect spread rate. Use the midpoint for planning and round up when buying.

Paint Type	Interior Walls (sq ft/gal)	Exterior Walls (sq ft/gal)	Trim / Doors (sq ft/gal)	Notes
Latex flat	350–400	300–350	—	Highest coverage; hides imperfections
Latex eggshell	350–400	300–350	—	Slight sheen; easy to clean
Latex satin	350–400	300–350	250–300	Good for kitchens, baths, and hallways
Latex semi-gloss	300–350	275–325	200–300	Durable; standard for trim and doors
Latex gloss	300–350	275–325	200–250	Hardest finish; cabinets and high-wear trim
Oil-based (alkyd)	350–400	300–350	200–300	Smooth leveling; longer dry time
Primer (PVA)	350–400	—	300–350	New drywall and joint compound
Primer (bonding)	300–350	250–300	250–300	Glossy or slick surfaces
Primer (stain-blocking)	300–350	250–300	250–300	Smoke, water, or tannin stains
Exterior elastomeric	—	100–200	—	Thick coating for stucco crack bridging

Reading the chart: If you are painting interior bedroom walls with latex eggshell, plan for 375 sq ft per gallon (the midpoint of 350–400). For two coats on 500 sq ft of wall, you need 500 × 2 ÷ 375 = 2.67 gallons — buy 3 gallons.

Factors Affecting Paint Coverage

Coverage per gallon is not a fixed number. These factors push it higher or lower:

Surface texture. Smooth primed drywall: 350–400 sq ft/gal. Light texture (orange peel, knockdown): 300–350 sq ft/gal. Heavy texture (popcorn, stucco, brick): 200–300 sq ft/gal. Rougher surfaces have more area to fill.
Paint finish. Flat and eggshell finishes spread thinner and cover more area. Semi-gloss and gloss finishes build a thicker film and cover less per gallon.
Paint quality. Premium paints with higher solids content cover more in fewer coats. Budget paints may require an extra coat, which offsets the lower price.
First coat vs second coat. The first coat on bare or porous surfaces absorbs into the substrate, reducing coverage. The second coat sits on a sealed surface and goes further. Plan your gallon count based on the first-coat rate to avoid running short.
Surface condition. New drywall, raw wood, and patched areas absorb more paint. Previously painted walls in good condition give the best coverage. Dark-to-light color changes may need an extra coat or a tinted primer.
Application method. Rollers use paint efficiently on large surfaces. Brushes use more paint per square foot but are necessary for cutting in and detail work. Sprayers cover fast but can waste 20–30% of material through overspray if not controlled.
Humidity and temperature. Painting in high humidity or extreme heat causes paint to dry too fast or too slow, affecting spread rate and adhesion. Exterior painting is especially sensitive to weather conditions.

Interior vs Exterior Coverage Differences

Interior walls are usually smooth drywall or plaster — flat, sealed surfaces that let paint spread evenly. That is why interior coverage runs 350–400 sq ft per gallon. The paint sits on top of the surface rather than soaking in.

Exterior surfaces are rougher, more porous, and more varied. Wood siding has grain. Stucco has texture. Brick has mortar joints. These surfaces absorb more paint and require thicker coats for weather protection, which is why exterior coverage drops to 250–350 sq ft per gallon.

Surface	Interior Rate (sq ft/gal)	Exterior Rate (sq ft/gal)	Why the Difference
Smooth drywall / plaster	350–400	—	Sealed, flat surface
Textured drywall	250–350	—	Peaks and valleys increase surface area
Wood siding (smooth)	—	300–350	Moderate grain absorption
Wood siding (rough-sawn)	—	250–300	Heavy grain pulls paint in
Vinyl / aluminum siding	—	350–400	Non-porous; paint sits on top
Stucco	—	200–275	Heavy texture; deep absorption
Brick	—	200–250	Porous masonry; mortar joints
Concrete block	—	200–275	Porous; uneven surface

Exterior paints are also formulated differently — they contain UV stabilizers, mildewcides, and flexible binders that add thickness to the film. This thicker film provides weather resistance but reduces how far each gallon stretches.

Coverage for Trim, Doors, and Windows

Trim paint (semi-gloss or gloss) covers 200–300 square feet per gallon on smooth wood or MDF. Trim has less surface area than walls, but the paint goes on thicker for durability and sheen, so coverage per gallon is lower.

To calculate trim square footage, convert linear feet to square feet:

Baseboards: Linear feet × board height. Example: 100 linear feet of 5.5-inch baseboard = 100 × (5.5 ÷ 12) = 45.8 sq ft. At 250 sq ft/gal, that is about 0.18 gallons per coat — one quart handles two coats.
Door casing: Each side of a standard door casing is about 17 linear feet × 2.5 inches wide = 3.5 sq ft. A full door surround (both sides, head) is roughly 7 sq ft.
Window casing: Similar to doors but shorter. A standard window surround is about 5 sq ft.
Crown molding: Linear feet × face width. 50 feet of 3.5-inch crown = 50 × (3.5 ÷ 12) = 14.6 sq ft.

Door coverage: A standard interior door is about 20 sq ft per side (both faces). One gallon of semi-gloss covers 10–15 door sides depending on the wood grain and whether the door is primed. A 6-panel door uses slightly more paint than a flat slab door because the panels add surface area.

For trim board widths, the lumber dimensions chart lists actual vs nominal sizes. A “1x6” baseboard is actually 5.5 inches wide — use the actual dimension for accurate area calculations. The fraction to decimal chart helps convert tape measure readings when measuring trim dimensions in the field.

Paint Coverage Calculator

The fastest way to turn coverage rates into a gallon count is to use the paint calculator on OnSiteCalculator. Enter your room dimensions, number of doors and windows, surface type, and number of coats, and the calculator does the math.

If you prefer to calculate by hand, here is the formula:

Gallons = (Paintable Area × Number of Coats) ÷ Coverage Rate per Gallon

Step by step:

Measure paintable area. Walls: height × width for each wall. Ceiling: length × width. Trim: linear feet × board width.
Subtract openings. Deduct 20 sq ft per standard door and 15 sq ft per window from wall area.
Multiply by coats. Two coats is standard. New surfaces or dark-to-light changes may need three.
Divide by coverage rate. Use the chart above for your paint type and surface. Use the midpoint of the range.
Add waste. Add 5–10% for rollers and brushes, 20–30% for sprayers.
Round up to the nearest whole gallon.

Example — interior bedroom (12 x 14, 8-foot ceilings):

Wall area: (12 + 14 + 12 + 14) × 8 = 416 sq ft
Subtract 1 door (20 sq ft) + 2 windows (30 sq ft) = 366 sq ft
Two coats: 366 × 2 = 732 sq ft
At 375 sq ft/gal (latex eggshell midpoint): 732 ÷ 375 = 1.95 gallons
Buy 2 gallons

Example — exterior stucco wall (40 × 10):

Wall area: 400 sq ft
Subtract 3 windows (45 sq ft) = 355 sq ft
Two coats: 355 × 2 = 710 sq ft
At 237 sq ft/gal (stucco midpoint): 710 ÷ 237 = 3.0 gallons
Buy 3 gallons (add a 4th if the stucco is deeply textured)

Paint Calculator — Enter room dimensions and get an instant gallon estimate for interior or exterior projects with waste and primer calculations.
Drywall Calculator — Estimate sheets and finishing materials for new drywall before priming and painting.
Flooring Calculator — Calculate square footage for rooms you are also painting.
Fraction to Decimal Chart — Convert tape measure fractions to decimals when measuring trim widths and wall dimensions.
Lumber Dimensions Chart — Look up actual board widths for baseboards, casings, and crown molding.
How to Read a Tape Measure — Learn to read fraction marks on your tape for accurate wall and trim measurements.
Measurement Accuracy Guide — Choose the right precision level for your paint measuring and layout work.

Frequently Asked Questions

Common questions about paint coverage rates, gallon estimates, and how surface type affects how much paint you need.

What is paint coverage per gallon for interior walls?

One gallon of interior latex paint covers 350–400 square feet on smooth, primed drywall in a single coat. Flat and eggshell finishes tend toward the higher end (400 sq ft), while semi-gloss and gloss finishes cover slightly less due to thicker film build. On textured or unpainted surfaces, coverage drops to 250–350 sq ft per gallon.

What is paint coverage per gallon for exterior walls?

Exterior paint covers 250–350 square feet per gallon depending on the surface. Smooth wood siding and panels are at the higher end (300–350 sq ft). Stucco, brick, and rough-sawn wood are at the lower end (200–300 sq ft) because the texture absorbs more paint.

How much area does 1 gallon of paint cover?

For a single coat on smooth interior walls, expect 350–400 square feet per gallon. For two coats on the same surface, one gallon covers about 175–200 square feet of finished wall. Exterior and textured surfaces reduce these numbers. Always check the coverage rate printed on the paint can label for your specific product.

Does paint coverage change for the second coat?

The second coat typically covers more area per gallon than the first because the surface is already sealed and less absorbent. However, you should still plan for the same coverage rate when buying paint. Under-buying by assuming the second coat stretches further is a common mistake that leads to mid-project store runs.

How much paint do I need for textured walls?

Textured walls like knockdown, orange peel, or popcorn reduce coverage to 250–300 square feet per gallon because paint fills the peaks and valleys of the texture. Use the lower end of the coverage range and add 10–15% waste when estimating for heavily textured surfaces.

What is paint coverage per gallon for trim and doors?

Trim paint (usually semi-gloss or gloss) covers 200–300 square feet per gallon on smooth wood or MDF. Doors average about 20 square feet per side, so one gallon covers roughly 10–15 door sides. Baseboards and casings are calculated by converting linear feet to square feet using the board width.

Paint Coverage Per Gallon Summary

This guide provides coverage rates per gallon for every common paint type and surface combination. Use the charts and examples alongside the paint calculator on OnSiteCalculator to estimate exactly how many gallons your project needs.

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