Ceiling Paint Calculator

By Vinod Kondeti · Updated October 14, 2026

A flat ceiling has the same area as the floor: length × width. Ceilings are usually painted separately from walls, often with a dedicated ceiling paint, so this calculator keeps them separate and lets you use that product's coverage figure.

Room length (ft)Room width (ft)Coats (coats)Coverage per gallon (from label) (ft²)Add one coat of primerPrimer coverage per gallon (from label) (ft²)

Cost estimate (optional, enter your local prices)

Paint price per gallon ($)Primer price per gallon ($)

Paintable area (ft²)	–
Paint gallons needed	–
Paint to buy	–
Primer gallons	–
Primer to buy	–
Estimated cost (whole gallons)	–

Working: –

How do I measure for a ceiling project?

For a sloped or vaulted ceiling, measure along the slope, or use the triangle calculator for gable sections.
Popcorn and textured ceilings soak up more paint, so use a lower coverage figure.
Enter the coverage printed on your ceiling paint.

How is the ceiling amount calculated?

Room walls = 2 × (length + width) × height − doors & windows (+ length × width for the ceiling)
Gallons = area × coats ÷ coverage per gallon (default 350 ft²)
To buy = gallons rounded up to whole quarts (4 qt = 1 gal)
Exterior = perimeter × wall height + gables × ½ × width × height − openings
Openings = doors × area per door + windows × area per window + other
Primer (optional) = one coat: area ÷ primer coverage
Cost = whole gallons × your $/gal (paint + primer)

Ceiling calculator questions

How much paint for a 12 × 12 ceiling, one coat?

144 ÷ 350 = 0.41 gal, so 2 quarts.

Two coats on a 15 × 20 ceiling?

300 × 2 ÷ 350 = 1.71 gal, so 1 gallon + 3 quarts.

Sources

Estimates only. Use the coverage or bag size printed on your product. Read the paint guide for worked examples.