Painting Calculators

Paint and primer coverage math for interior walls, ceilings, and exterior surfaces. Our painting calculators handle door and window deductions, coat multipliers, primer-versus-paint coverage, and gallon-to-liter conversions automatically.

Paint estimating seems simple until you account for all the variables. Coverage varies by surface texture, primer type, paint quality, application method, color change depth, and even humidity. A single-coat repaint of a small bathroom needs a fraction of what a dark-to-light color change requires. Skipping primer on new drywall means your first gallon soaks in like water on a sponge — the second coat looks uneven and the third barely fixes it. The calculators in this category bake in these realities so your material list matches your actual job site.

The Paint & Primer Coverage Calculator automatically deducts standard door and window areas from your wall surface, applies a coat multiplier, and converts between gallons and liters for users on either side of the Atlantic. Pair it with the Drywall Estimator to plan the full sequence from hang-and-finish through final coat — and save both estimates to your project basket for a combined materials budget.

Painting is the most accessible trade for DIYers but the one with the widest quality gap between amateur and professional results. The standards below will help you close that gap.

Paint Coverage Reference

• Premium interior latex (flat): 350–400 sq ft per gallon on smooth, primed walls.
• Premium interior latex (eggshell/satin): 300–350 sq ft per gallon (slightly lower due to sheen resin load).
• Builder-grade paint: 250–300 sq ft per gallon.
• Primer (acrylic latex): 350–400 sq ft per gallon.
• Primer (oil-based / PVA): 300–350 sq ft per gallon.
• Exterior paint (acrylic latex): 250–350 sq ft per gallon depending on surface porosity.
• Deck stain: 200–300 sq ft per gallon on rough wood; 300–400 on smooth.

Roller Nap Selection

• 1/4" nap: Gloss and semi-gloss on smooth surfaces (cabinets, doors, trim).
• 3/8" nap: Standard for smooth walls (eggshell, satin, flat on drywall).
• 1/2" nap: Medium textures (orange peel, light knockdown).
• 3/4" nap: Heavy textures (stucco, brick, rough plaster).
• 1" nap: Masonry and deeply textured surfaces.

Paint Sheen Guide

• Flat: Lowest sheen, hides imperfections, least washable. Best for ceilings and low-traffic walls.
• Matte: Slightly more washable than flat, similar look. Modern alternative to flat.
• Eggshell: Subtle sheen, washable. The residential standard for living areas.
• Satin: Noticeable sheen, very washable. Kitchens, baths, kids' rooms.
• Semi-gloss: High sheen, scrubbable. Trim, doors, cabinets, bathrooms.
• Gloss: Maximum sheen, mirror-like. Front doors, accent furniture. Shows every flaw.