How much paint do I need?

What Is Paint Coverage and Why Does It Matter?

Paint coverage refers to the number of square feet a single gallon of paint can coat in one application. The industry-standard figure is 350 square feet per gallon, though actual coverage depends on the paint type, surface texture, application method, and color. This number comes from manufacturers testing on smooth, primed drywall with a roller — real-world coverage is often slightly less.

Getting the coverage estimate right saves you money and trips to the store. Buy too little and you will run out mid-wall, leaving visible lap marks where wet paint overlaps dried paint. Buy too much and you have leftover cans taking up garage space for years.

Understanding Paint Sheens

The sheen (finish) you choose affects both appearance and coverage. Here is what to know about each:

• Flat / Matte: Hides surface imperfections well and provides the most coverage per gallon. Best for ceilings and low-traffic areas like formal dining rooms and adult bedrooms. Difficult to clean — marks and scuffs may require touch-up painting rather than wiping.
• Eggshell: A slight sheen that is easier to clean than flat. The most popular choice for living rooms, bedrooms, and hallways. Good balance of hide and durability.
• Satin: A soft, velvety sheen that resists moisture and cleans up easily. Ideal for kitchens, bathrooms, kids’ rooms, and high-traffic hallways. Slightly less coverage per gallon than flat due to the resin content.
• Semi-Gloss: A noticeable shine that is highly washable and moisture-resistant. Standard for trim, doors, cabinets, and bathrooms. Shows surface imperfections more than flatter sheens, so prep work matters.

When You Need More Than Two Coats

Two coats is the standard recommendation for most paint jobs, but certain situations require additional coats:

• Drastic color changes: Going from dark to light (or vice versa) can require 3–4 coats, even with a tinted primer. Red, orange, and deep yellow are notoriously difficult to cover in fewer than 3 coats.
• Unpainted drywall: New drywall is porous and absorbs the first coat almost entirely. Always use a dedicated primer first, then apply 2 coats of your finish color.
• Textured surfaces: Textured walls, stucco, and brick have more surface area than smooth drywall, requiring 15–25% more paint per coat.
• Going from gloss to flat: High-gloss surfaces require proper sanding and priming before repainting, and the flat paint may need an extra coat to look uniform.

When in doubt, buy an extra gallon. Leftover paint is useful for touch-ups, and most stores accept returns on unopened cans.

Primer: When You Need It and When You Do Not

Modern paint-and-primer combos have reduced the need for separate priming, but there are situations where a standalone primer is essential:

• Bare drywall or new construction: Always prime first. Drywall compound and paper absorb paint differently, and primer creates a uniform surface.
• Stains and odors: Water stains, smoke damage, and crayon marks bleed through regular paint. Use a stain-blocking primer (shellac-based for the toughest stains).
• Drastic color changes: A gray-tinted primer under dark colors or a white primer under light colors reduces the number of finish coats needed.
• Glossy surfaces: Sand lightly and apply a bonding primer before painting over semi-gloss or gloss finishes.

Primer coverage is similar to paint — approximately 300–400 square feet per gallon depending on the surface. Factor this into your total paint budget.

Ceiling Paint: A Separate Calculation

Ceilings are calculated separately from walls. Multiply the room’s length by its width to get the ceiling area in square feet, then divide by 350. Ceiling paint is formulated to be thicker and more spatter-resistant than wall paint, and it typically only needs one coat unless you are covering a dark color. A 12×12 room has a 144 sq ft ceiling — well under one gallon.

Buying Tips to Save Money

Smart paint shopping can save you 20–40% without sacrificing quality:

• Buy in 5-gallon buckets: Per gallon, a 5-gallon bucket costs 10–20% less than five individual gallons. If your project needs 4+ gallons of the same color, buy the bucket.
• Watch for sales: Major paint manufacturers run sales 3–4 times per year, typically around holiday weekends (Memorial Day, Labor Day, Black Friday). Savings of $10–$15 per gallon are common.
• Mis-tint shelves: Most stores sell mis-tinted paint at 50–75% off. If you are flexible on color, check the mis-tint shelf first.
• Do not overbuy: Use this calculator to get the right amount. One extra gallon for touch-ups is smart; five extra gallons is waste.

How to Estimate Paint for Trim and Doors

Trim and doors are typically painted with a different sheen (semi-gloss) than the walls. Here are quick estimates for standard sizes:

• Standard interior door: About 20 square feet per side (both sides = 40 sq ft)
• Window trim: About 10 square feet per window (frame and casing)
• Baseboard trim: Multiply the room perimeter by the baseboard height (typically 0.33–0.5 feet)
• Crown molding: Multiply the room perimeter by the molding width (typically 0.25–0.5 feet)

For a typical bedroom, trim and doors combined require about 1 gallon of semi-gloss paint for two coats.