Ceiling Paint Calculator

How it works

A flat ceiling's area is its length times its width. For several rooms of the same size the calculator multiplies by the number of rooms; ceilings of other sizes can be added as extra square feet.

The area is multiplied by the number of coats and divided by the coverage of one gallon. Ceiling paint data sheets quote coverage for a smooth surface, and add that the actual rate depends on surface texture and porosity. Textured and popcorn ceilings have far more surface than their flat footprint and soak up more paint, so the coverage is reduced by the percentage for the chosen texture before dividing.

The texture reductions offered (20% for light texture, 30% for heavy texture or popcorn) are typical allowances, not figures published by a manufacturer. Choose Custom to enter your own.

Formula

ceiling area       = length × width × rooms + other ceiling area
total area         = ceiling area × coats
coverage used      = coverage per gallon × (1 − texture reduction ÷ 100)
paint needed (gal) = total area ÷ coverage used
gallons to buy     = paint needed, rounded up

Example

A 12 ft × 14 ft smooth ceiling is 168 sq ft. Two coats means covering 336 sq ft. At 400 sq ft per gallon that is 0.84 gallon, so 1 gallon to buy.

The same ceiling with popcorn texture: coverage falls by 30% to 280 sq ft per gallon, and 336 ÷ 280 = 1.2 gallons, so 2 gallons to buy.

Assumptions and limitations

• Ceilings are flat rectangles. Sloped, vaulted and tray ceilings have more area than length × width; their measured area can be entered as other ceiling area.
• Coverage is a typical value and editable. Ceiling paint data sheets give a range, and the manufacturer states the actual spread rate depends on surface texture and porosity.
• The 20% and 30% texture reductions are typical allowances, not manufacturer figures; the paint on a given texture can differ.
• Bare or stained ceilings may need a primer, which is not included. The US EPA lists textured paint and patching compounds used on walls and ceilings among the places asbestos may be found (EPA, Learn About Asbestos, updated July 2026). This calculator says nothing about whether a ceiling is safe to disturb; that is a matter for testing and official guidance.
• The result is an estimate and not a substitute for the paint manufacturer's instructions.

Frequently asked questions