How much paint do I need for a room?

It depends on total paintable square footage, number of coats, and the coverage rate on your paint label—often around 350 sq ft per gallon on smooth surfaces, but always verify the can. Use the calculator with your measurements for a starting estimate.

How many gallons of paint for a 12x12 room?

A 12×12 ft room with 8 ft ceilings has roughly 384 sq ft of wall area if you paint all four walls, plus 144 sq ft if you include the ceiling. Enter those figures, subtract doors and windows, set your coat count, and adjust coverage to match your product.

Should I buy extra paint?

Most projects benefit from a small waste allowance for touch-ups and cutting mistakes—often 10% for walls, more for complex layouts. Store leftover labeled paint for future repairs.

Paint Coverage Calculator

Buying too little paint delays your project; buying too much wastes money. This calculator estimates quantity based on the paintable area you enter, the number of coats, and the coverage rate on your paint label.

Results are planning estimates only. Actual coverage varies by paint product, surface texture, color change, primer use, and application method. Always check the specific can you plan to buy before purchasing.

How it works

Paintable area equals wall area plus ceiling area, minus the square footage of doors and windows. Total paint needed equals paintable area multiplied by the number of coats, plus your waste percentage, divided by the coverage rate (square feet per gallon). Litres are converted from gallons using 3.785 L per gallon.

What affects paint coverage?

Coverage on the label assumes a smooth, primed or previously painted surface applied at the recommended thickness. Textured walls, porous drywall, bare joint compound, and dramatic color changes (especially light over dark) often need more coats or more product per coat.

Spraying, rolling, and brushing use paint differently. Cut-in work around trim adds time and can slightly increase total volume compared to wide wall areas alone.

How to measure a room for painting

Measure each wall length and multiply by ceiling height for wall area. Add ceiling length × width if you are painting the ceiling. Subtract rough allowances for doors and windows, or count each opening using the adjustable defaults in the calculator.

For step-by-step measuring tips and common mistakes, see our guide on how to measure a room for painting.

Important limitations

This tool does not account for textured walls, drastic color changes requiring extra coats, separate primer quantities, or trim paint. It does not replace the coverage figure on your paint can. Rough or porous surfaces may need more product than the label suggests.

Estimates are for planning only—not a guarantee of how much paint you must buy.

What to do next

Verify measurements on site, read your paint label for coverage, buy slightly more if cutting in complex trim, and review our guides on measuring rooms and surface prep before you start.

Frequently asked questions

How much paint do I need for a room?: It depends on total paintable square footage, number of coats, and the coverage rate on your paint label—often around 350 sq ft per gallon on smooth surfaces, but always verify the can. Use the calculator with your measurements for a starting estimate.
How many gallons of paint for a 12x12 room?: A 12×12 ft room with 8 ft ceilings has roughly 384 sq ft of wall area if you paint all four walls, plus 144 sq ft if you include the ceiling. Enter those figures, subtract doors and windows, set your coat count, and adjust coverage to match your product.
Should I buy extra paint?: Most projects benefit from a small waste allowance for touch-ups and cutting mistakes—often 10% for walls, more for complex layouts. Store leftover labeled paint for future repairs.

Room Area Calculator
Calculate room square footage in feet or meters—for flooring, paint prep, or material estimates.
Flooring Calculator
Calculate floor area with a customizable waste percentage for flooring projects.