Paint estimating hub: gallons, coverage and costs
Most paint questions come down to three numbers: the paintable square footage, the coverage per gallon on your surface, and the number of coats. This hub gathers our paint calculator, coverage guides and room-by-room articles so you can buy the right number of gallons the first time.
Start hereUse the free Paint CalculatorEstimate paintable wall area and how many gallons of paint your project needs.Quick checklist
- Paintable wall area (sq ft) = sum of each wall's length (ft) × height (ft), minus the measured area of openings you will not paint.
- Coated area (sq ft) = paintable area × the number of coats specified for your chosen paint and surface.
- Gallons needed = coated area ÷ the product's coverage (sq ft per gallon); round up to the can sizes available. Sherwin-Williams cites about 350–400 sq ft per gallon as a typical range, but check your product label and surface condition.
- If priming, calculate primer separately using its own labeled coverage and coat count; do not count primer as a paint coat.
Calculators for paint projects
- Paint CalculatorEstimate paintable wall area and how many gallons of paint your project needs.
- Home Renovation Cost CalculatorBuild a transparent renovation budget from your own material, labor and contingency inputs.
- Flooring CalculatorWork out square footage and how many boxes of flooring to order, including waste.
In-depth guides
- How Much Paint Do I Need?
Add the length of every wall, multiply by ceiling height, subtract door and window openings, then divide by the paint's coverage rate (commonly 350-400 sq ft per gallon) and multiply by the number of coats. A typical 12 x 12 ft bedroom needs roughly 1.5-2 gallons for two coats.
Articles from the blog
- How Much Paint Do I Need to Paint a Room?One gallon covers about 350 square feet per coat. Everything else is measuring walls properly and being honest about how many coats you need.
- How Much Does a Gallon of Paint Cover?Labels say 400 square feet per gallon; textured walls and color changes say otherwise. Here is how to plan paint quantity that doesn't run short.
- How Much Exterior Paint Do I Need for a House?Siding texture, not house size, drives paint consumption. Rough cedar can drink a third more than smooth fiber cement over the same wall.
Common questions
- How many square feet does a gallon of paint cover?
- About 350–400 sq ft per coat on smooth, primed walls; textured or porous surfaces often get 250–300 sq ft.
- How many coats do I need?
- Two coats for a color change or new drywall; one coat can work when refreshing the same color.
- Should I subtract doors and windows?
- Yes — roughly 20 sq ft per door and 15 sq ft per window is a common allowance.
Not sure which tool fits your project? Describe it to the Project Advisor.