Short answer
A 1,500 sq ft single-story ranch house with a 160 ft perimeter, 10 ft walls, 3 exterior doors, and 10 windows requires approximately 8 gallons of body paint for two coats. That's based on 1,387 sq ft of paintable wall area at 350 sq ft per gallon. You'll also need about 4 gallons of primer (if priming) and 6 quarts of trim paint.
How this calculator works
The calculator starts with gross wall area — perimeter multiplied by wall height — then subtracts openings. Each exterior door deducts 21 sq ft (a standard 3×7 ft door), and each window deducts 15 sq ft (a typical double-hung). For this variant:
Gross wall area: 160 ft × 10 ft = 1,600 sq ft
Door deductions: 3 doors × 21 sq ft = 63 sq ft
Window deductions: 10 windows × 15 sq ft = 150 sq ft
Paintable wall area: 1,600 − 63 − 150 = 1,387 sq ft
From there, the formula multiplies by the number of coats and the siding factor, then divides by 350 — the industry-standard coverage rate for quality exterior paint in sq ft per gallon.
Body paint: (1,387 × 2 coats × 1.0 siding factor) ÷ 350 = 7.93 gallons, rounded up to 8 gallons
What the siding factor does
Smooth siding (hardboard, fiber cement) uses a factor of 1.0. Vinyl lap siding with deeper channels uses 1.1, adding about 10% more paint to fill the texture. Cedar shake and stucco get a 1.2 factor — a 20% increase — because their surface area is significantly higher than the measured flat dimension. If you're painting rough-sawn wood or deeply weathered siding, the 1.2 factor is the safer choice.
Secondary outputs explained
Primer (4 gallons): Calculated at one coat using the same 350 sq ft coverage rate. Primer is not always required — if you're recoating with the same color and paint type in good condition, you can skip it. It's necessary for bare wood, patched areas, stain blocking, or major color changes.
Trim quarts (6 quarts): Estimated at 1 quart per 30 linear feet of perimeter. This covers fascia boards, corner boards, window casings, door casings, and any decorative trim running around the perimeter. The 160 ft perimeter ÷ 30 = 5.3, rounded up to 6 quarts. If your house has extensive built-up cornice work or wide corner boards, add another quart or two.
Coverage rate and real-world variation
The 350 sq ft per gallon rate is a conservative middle ground. Some premium paints advertise 400 sq ft/gallon on smooth surfaces, but that's under ideal conditions. Roller nap thickness, surface porosity, temperature, and how liberally you apply all reduce real coverage. For rough or thirsty surfaces, 300 sq ft/gallon is more realistic. The 10% default waste factor built into most exterior paint jobs accounts for roller overlap, loading the brush, and minor spills.
What this calculator does not include
- Porch ceilings or soffits (measure and add separately)
- Detached garages or outbuildings
- Masonry foundation walls (use a masonry sealer estimate instead)
- Shutters (typically painted separately, 1 quart handles 8–10 standard shutters)
For gable ends on a two-story or story-and-a-half house, increase the wall height input to the average height including the gable, or calculate the gable triangles separately and add that area to the perimeter × height total.
Recommended materials
For a ranch this size, two coats of a self-priming exterior paint cuts total material and labor compared to a separate prime-and-paint sequence. If you're rolling by hand, satin or low-luster finish hides roller marks better than flat on most sidings. For spraying, thin per the manufacturer's spec — typically 10% for airless application. Here are the products worth having on hand:
- Behr Marquee exterior paint (1 gallon) — self-priming formula with solid hide; rated for 400 sq ft/gallon on smooth surfaces
- Graco Magnum X5 airless paint sprayer — handles full gallons, suitable for a house this size; cuts application time versus rolling
- Werner D1224-2 24-foot aluminum extension ladder — reaches eaves and fascia on a single-story with standard 9–10 ft ceilings; the 24 ft length gives safe working height at the top of the extension
FAQ
How many gallons of paint do I need for a 1500 sqft single-story ranch?
With a 160 ft perimeter, 10 ft walls, 3 doors, and 10 windows, you need approximately 8 gallons of body paint for 2 coats. That covers 1,387 sq ft of paintable wall surface at 350 sq ft per gallon per coat.
Does the 1,500 sq ft floor area equal 1,500 sq ft of paintable wall?
No. Floor area and wall area are different measurements. Wall area depends on perimeter and wall height, minus doors and windows. A 1,500 sq ft ranch with a 160 ft perimeter and 10 ft walls has roughly 1,387 sq ft of paintable surface.
How much primer do I need for this house?
One coat of primer requires about 4 gallons. Primer is recommended whenever you're making a significant color change, painting raw or repaired siding, or switching paint types.
How many quarts of trim paint will I need?
The calculator estimates 6 quarts for a house with a 160 ft perimeter. The rule of thumb is 1 quart per 30 linear feet of trim, covering fascia, corner boards, window casings, and door trim.
What siding factor should I use for my house?
Use 1.0 for smooth LP or hardboard siding, 1.1 for vinyl or wood lap siding with pronounced texture, and 1.2 for stucco or cedar shake. Rougher surfaces absorb more paint and require more material.
Should I buy exactly 8 gallons or round up?
Round up to 9 gallons. The formula uses 350 sq ft per gallon as a standard coverage rate, but real-world application, roller nap, and surface absorption can reduce coverage. Having an extra gallon also lets you touch up later with the same batch.
Does two coats mean I double the paint needed?
Yes, the calculator already accounts for the number of coats. The 8-gallon figure is the total for both coats, not per coat.
Can I use the same paint for trim and the body of the house?
You can use the same color, but trim typically gets a higher-sheen finish (semi-gloss or gloss) for durability and visual contrast. Body paint is usually satin or low-luster. Buying separate products gives you that flexibility.
How do I measure my house perimeter if I don't have plans?
Walk the perimeter with a 100 ft measuring tape, measuring each exterior wall and adding them together. For L-shaped or complex footprints, break the house into rectangles and sum all exterior wall lengths.
Does this calculator include garage doors?
The door deduction uses 21 sq ft per door, which approximates a standard 3×7 ft entry door. For a two-car garage door (roughly 126 sq ft), count it as 6 doors or subtract its area manually before entering the input.
How much does it cost to paint a 1500 sqft ranch house?
Material cost depends on the paint you choose. At roughly 8 gallons of body paint plus 6 quarts of trim paint, budget for 9–10 gallons of quality exterior paint and 6–7 quarts of trim paint. Labor for professional painters varies widely by region and is not included here.
What's the best time of year to paint exterior siding?
Most exterior paints require temperatures between 50°F and 90°F with low humidity. Late spring and early fall are typically ideal. Avoid painting in direct midday sun, which causes the paint to dry too fast and reduces adhesion.