Exterior House Paint Estimate: Walls, Gables, Trim, and Gallons Needed

Subtract Openings and Add Coats

Windows and doors reduce the painted area: a typical window is 15 square feet and a door 21. With, say, 10 windows and 2 doors, the openings total 192 square feet, which we round to 200. Net siding area is 1,485 − 200 = 1,285 square feet. At two coats, the paint required is 2,570 square feet. At 350 square feet per gallon on smooth surfaces, that is 7.3 gallons, so buy 8 gallons (or 1 five-gallon pail plus 3 gallons). Use a coverage rate of 250 to 300 for rough surfaces and bare wood. If you are painting over a similar color on a previously painted surface, one coat of a high-quality paint may suffice, which would halve the amount.

Windows with many panes and trim may still require painting around them, so many painters subtract openings only if large.

Trim, Doors, and Soffits

Trim, fascia, soffits, and doors use a different color and sheen and are estimated separately. A rough method is to measure linear feet of trim and multiply by its width: 280 feet of 5.5-inch fascia and corner boards is 128 square feet. A front door is about 21 square feet per side. A gallon of trim paint covers 350 square feet, so a gallon is plenty for 300 square feet of trim and doors on two coats. Soffits are often 12 to 24 inches wide, with an area equal to the perimeter times the width: 140 feet × 1.5 feet = 210 square feet. Add a quart or a gallon of trim paint for a typical house.

Primer and Preparation

New wood, bare patches, and stained areas need primer. Primer coverage is similar to paint, about 300 to 400 square feet per gallon, but use only where necessary to save money. Preparation is usually the most time-consuming part: pressure wash, scrape loose paint, sand edges, fill holes, replace rotten wood, and caulk gaps. Paint adheres poorly to dirty or damp surfaces; wait for dry weather. Lead paint may be present in homes built before 1978 in the United States, and special safety procedures apply to scraping and sanding. Test before disturbing old paint.

Buying and Application Tips

Buy a bit extra for touch-ups, and keep the label for color matching. Choose 100% acrylic exterior paint for durability and flexibility. Apply when temperatures are between 50 and 90 degrees Fahrenheit and no rain is expected for 24 hours. Work from top to bottom, and in the shade where possible to avoid rapid drying and lap marks. Spraying is faster than rolling and brushing, but requires masking and often back-brushing. A professional painter may charge $2 to $4 per square foot of siding, whereas materials typically cost $200 to $600 for a house this size.