Paint Calculator
Enter your room size, coats, and how many doors and windows to skip — get the paintable square footage and how many gallons to buy.
Room
You'll need
Paintable area0 sq ft
Total surface (2 coats)0 sq ft
Paint to buy
0 gallons
at 350 sq ft per gallon
Estimate only. Primer, dark-to-light color changes, and porous or textured surfaces use more.
How much paint do I need?
Find the wall area — 2 × (length + width) × height — subtract about 21 sq ft per door and 15 sq ft per window, multiply by the number of coats, then divide by the coverage on the can (usually 350–400 sq ft per gallon). Round up to the next whole gallon.
Quote a paint job on-site in minutes
ProBuildCalc turns your iPhone's LiDAR scanner into a job-site measuring kit — walk the space and it captures the square footage, material takeoff, and a blueprint automatically. No tape measure, no graph paper.
Paint calculator FAQ
- How much area does a gallon of paint cover?
- A gallon covers roughly 350–400 square feet in one coat on a smooth, primed surface. Textured, porous, or unprimed walls absorb more, so they cover less per gallon.
- How many coats of paint do I need?
- Plan on 2 coats for most jobs — it's the default here. Use 3 when going from a dark color to a light one or painting over bare drywall; 1 coat is only enough for a light refresh of the same color.
- Do I subtract doors and windows?
- Yes. Each standard door is about 21 sq ft and each window about 15 sq ft of surface you don't paint. Enter the counts above and they're deducted automatically.
- How do I calculate wall area for paint?
- Add the length of all walls (the room perimeter) and multiply by the ceiling height: 2 × (length + width) × height. The calculator does this from your room dimensions.