To calculate how much paint you need for exterior walls, measure and add each wall’s total square footage. You’ll include windows and doors, so don’t worry about trying to subtract those out.
Next, you’ll divide by 90% of the coverage provided by each can. For example, one gallon of paint can usually cover up to 400 square feet. For trim, you’ll add the total length of all trim and divide by 2.
When painting the exterior of your home, consider trying a paint sprayer for more control and a cleaner-looking finish. Start by loading the paint sprayer and work your way from the top down. Work in a slow, smooth motion being sure to overlap each stroked by about eight inches. Applying two coats will give you the best color that will last against outside elements.
Next, remove plastic sheeting from doors, windows, and landscaping, so you can paint the trim. You'll want to add two coats to the trim as well. Semi-gloss is recommended for woodwork because it's more durable and brighter.