# Outside Paint Calculator Outside paint calculator for your home exterior. Enter perimeter, wall height, siding type, and coats to get gallons needed and estimated paint cost. ## What this calculates A house exterior looks uniform from the curb, but every square foot of siding, trim, and soffit adds up fast. Use this outside paint calculator to convert your home's perimeter and wall height into a gallon estimate, accounting for siding texture and the doors and windows you won't be painting. The result tells you exactly how many gallons of outside paint to buy and what it will cost at your chosen grade. ## Inputs - **House Perimeter** (ft) — min 0 — Sum of all exterior wall lengths. For a 40x30 house: 2x(40+30) = 140 ft. - **Wall Height** (ft) — min 6, max 40 — Foundation to eave. One-story: 8-10 ft, two-story: 18-20 ft. - **Siding Surface** — options: Smooth (fiber cement, sealed stucco), Lap siding (vinyl, wood lap, hardboard), Rough sawn wood / board and batten, Stucco / textured masonry, Brick / CMU block - **Number of Coats** — min 1, max 4 — Two coats standard. Three for major color changes or faded old paint. - **Paint Grade** — options: Economy ($30/gal), Standard acrylic ($55/gal), Premium / 25-year ($80/gal) - **Exterior Doors** — min 0, max 20 — Each door subtracts ~21 sq ft - **Windows** — min 0, max 50 — Each window subtracts ~15 sq ft ## Outputs - **Gross Wall Area** (ft²) - **Paintable Area** (ft²) — After subtracting doors and windows - **Gallons Needed** - **Gallons to Order** — Rounded up to whole gallons - **Estimated Paint Cost** — formatted as currency ## Details ## How Much Outside Paint Do You Need The formula converts your home's perimeter and wall height into gross wall area, subtracts door and window openings, then divides by coverage per gallon. One gallon of exterior acrylic covers about **300 square feet on smooth siding** and less on rougher surfaces. | Siding | Coverage per gallon | |---|---| | Fiber cement (smooth) | 300 sq ft | | Vinyl or wood lap | 273 sq ft | | Rough sawn / board and batten | 214 sq ft | | Stucco | 231 sq ft | | Brick or CMU | 222 sq ft | ## Measuring Your Home Exterior Walk the perimeter of your house with a tape measure or pace it off if you already know the footprint. A rectangular 40x30 ft home has a perimeter of 140 linear feet. Multiply by wall height: 9 ft for a single-story to the eave, 18-20 ft for a two-story. That gives you gross wall area. Subtract 21 sq ft for each exterior door and 15 sq ft for each standard window. The result is your paintable area. ## Worked Example A 2,000 sq ft two-story with a 160 ft perimeter and 18 ft walls has **2,880 sq ft gross wall area**. Subtract 2 doors (42 sq ft) and 12 windows (180 sq ft) and you're left with **2,658 sq ft of paintable siding**. For two coats on lap siding (273 sq ft/gal effective), that's 2,658 x 2 / 273 = **19.5 gallons**. Order 20 gallons. ## Paint Grade Economics Premium exterior paint costs $80/gal but carries a 25-year warranty and actually lasts 15-20 years in real use. Economy paint at $30/gal lasts 5-7 years. On a 20-gallon job, premium costs $1,000 more upfront but saves you from repainting in 5 years. For any home you plan to keep, premium is the cheaper long-term choice. ## When to Paint Outside Paint when the surface and air temperature are both 50-85 degrees F, humidity is below 85%, and no rain is forecast for 24 hours. Avoid midday sun on hot days. Spring and early fall hit these conditions most reliably in most climates. ## Prep Is Half the Job Pressure wash first to remove chalking, mildew, and loose paint. Scrape any peeling areas, spot-prime bare wood, and caulk gaps around trim and windows. Skipping prep is the single biggest reason exterior paint jobs fail early. ## Frequently Asked Questions **Q: How do I calculate how much outside paint I need?** A: Measure the perimeter of your house, multiply by wall height to get gross wall area, subtract 21 sq ft per door and 15 sq ft per window, then divide by coverage per gallon (300 sq ft smooth, 273 for lap siding, 214 for rough wood) and multiply by the number of coats. A 40x30 single-story with 9 ft walls, 2 doors and 10 windows needs about 9-10 gallons for two coats on lap siding. **Q: How many gallons of outside paint to cover a house?** A: Most single-story homes (1,500-2,000 sq ft) need 8-12 gallons for two coats. Two-story homes (1,800-2,500 sq ft) need 16-22 gallons. Large homes (3,000+ sq ft) or those with rough siding can exceed 25 gallons. Plan to buy one extra gallon for touch-ups later. **Q: How much does outside paint cost for a whole house?** A: Paint alone runs $300-1,600 for most homes: economy at $30/gal, standard at $55/gal, premium at $80/gal. A typical 18-gallon two-story job costs $540 in standard paint or $1,440 in premium. Add $100-200 for primer, caulk, rollers, tape, and drop cloths. Labor for a pro runs $1.50-4.00/sq ft on top. **Q: Do I need different paint for different siding types?** A: Most exterior acrylic latex paints work on wood, fiber cement, vinyl, and properly primed stucco. Masonry and brick benefit from breathable masonry paint that lets moisture vapor escape. Always follow the manufacturer's substrate guide, and use a bonding primer when painting previously glossy or oil-based surfaces. **Q: Should I subtract windows and doors from wall area?** A: Yes. Each standard exterior door is about 21 sq ft and a typical window is 15 sq ft. On a home with 2 doors and 12 windows, that's 222 sq ft you won't be painting. Skipping this subtraction leaves you with 0.5-1 extra gallons, which is useful for touch-ups but wasteful if you already have leftovers. **Q: What temperature can I paint outside?** A: Standard exterior paint needs 50-85 degrees F surface and air temperature. Low-temp formulas (Sherwin Resilience, Benjamin Moore MoorGard Low Lustre) work down to 35 degrees. Always check the product data sheet. Avoid painting in direct sun on hot surfaces (over 90 degrees) because the paint can skin before it bonds. --- Source: https://vastcalc.com/calculators/construction/outside-paint Category: Construction Last updated: 2026-04-08