Miscellaneous
Paint Calculator - How Many Gallons Do I Need?
Calculate how much paint you need for a room. Enter room dimensions or direct wall area, subtract windows and doors, set coverage and coats, and get gallons rounded up to the nearest can.
Gross wall area
352.0 ft²
Deductions
51.0 ft²
Net wall area
301.0 ft²
Total (× coats)
602.0 ft²
Gallons needed
2 gal
(1.72 exact)
How much paint do I need?
Estimate wall area by adding all wall surfaces: 2 × (length + width) × height for a rectangular room. Then subtract windows (~15 sq ft each) and doors (~21 sq ft each) for a more accurate estimate.
Paint coverage
Coverage depends on paint quality and surface texture. Most interior paints cover 350–400 sq ft per gallon. Primers and flat paints may cover less (~250 sq ft/gal). Check the label before purchasing.
Coats and color changes
Two coats are standard. If you are painting a dark color over a light one (or vice versa), you may need three coats for complete coverage. High-hide "one-coat" paints can sometimes cover in one coat on similar colors.
Paint coverage reference
| Paint type | Coverage per gallon |
|---|---|
| Interior latex (flat/matte) | 350–400 sq ft |
| Interior latex (eggshell/satin) | 350–400 sq ft |
| Interior latex (semi-gloss/gloss) | 350–400 sq ft |
| Exterior paint | 250–300 sq ft |
| Interior primer | 200–300 sq ft |
| Exterior primer | 200–250 sq ft |
Ceiling and trim
This calculator covers walls only. For ceilings, measure length × width. Trim (baseboards, door frames, window casings) is often estimated at 0.1 gallons per window and 0.1 gallons per door from a separate quart can.
Texture effect on coverage
Smooth, newly-primed drywall gives the best coverage. Textured surfaces (orange peel, knock-down, popcorn ceilings) have significantly more surface area and will require 10–25% more paint. New drywall also absorbs more paint on the first coat; plan for a full prime coat before painting.