Paint Coverage Calculator

Determine exact gallons of wall paint, ceiling paint, and primer needed accounting for surface porosity and multiple coats.

Total Wall Perimeter (Ft) Sum of all 4 wall lengths

Ceiling Height (Ft)

Number of Paint Coats

Surface Porosity

Doors (21 sq ft ea)

Windows (15 sq ft ea)

Paint Gallons to Purchase

4 Gallons

540 sq ft Net Wall Area (2 Coats)

Primer Required 2 Gallons 1 coat base primer

Remaining Paint 0.9 Gal Save for future touch-ups

The 350 Sq Ft Standard Rule: One standard gallon of architectural interior latex paint covers approximately 350 to 400 square feet on primed drywall. Always purchase in whole gallons; buying multiple quarts is 50% more expensive per ounce.

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How Paint Coverage Is Calculated

Calculating paint begins with determining net paintable wall surface:

Gross Area = Perimeter × Height
Deductions = (Doors × 21 sq ft) + (Windows × 15 sq ft)
Net Area = Gross Area - Deductions
Gallons Needed = (Net Area × Number of Coats) / Coverage Rate per Gallon

Frequently Asked Questions

Do I really need two coats of paint if using "Paint & Primer in One"?

Yes. "Paint & primer in one" is marketing terminology for a higher-solids latex paint. While it has superior hide, two coats are required to achieve true manufacturer sheen uniformity and washability.

How much paint is needed for ceilings?

Multiply room length by width. A 14x20 ft room has 280 sq ft of ceiling, requiring 1 gallon of dedicated flat white ceiling paint for a single coat.

Why does raw unpainted drywall require more paint?

Bare gypsum paper and drywall joint compound soak up moisture like a sponge. Applying a dedicated PVA (polyvinyl acetate) primer seals the pores, preventing uneven sheen flashes.