How to Calculate Paint Coverage

Paint estimation involves calculating total wall area, subtracting doors and windows, and dividing by the coverage rate. Most paints cover about 350 sq ft per gallon.

The Formula

Gallons = (Wall Area - Openings) / Coverage per Gallon

Where:

Wall AreaWall Area — Total wall surface in square feet
OpeningsOpenings — Area of doors and windows
CoverageCoverage — Square feet per gallon (usually 350)

Step-by-Step Example

Here's how to calculate paint coverage step by step:

  1. 1Calculate wall area: Multiply perimeter by ceiling height for total wall area.
  2. 2Subtract openings: Subtract the area of doors (21 sq ft) and windows (15 sq ft each).
  3. 3Divide by coverage: Divide paintable area by 350 sq ft/gallon for the number of gallons.
  4. 4Multiply for coats: Multiply by 2 if you need two coats of paint.

Following these 4 steps gives you the final paint coverage value.

Skip the Math

A 12x14 ft room with 9 ft ceilings has 468 sq ft of walls; minus two windows and a door (51 sq ft) leaves 417 sq ft, needing about 1.2 gallons per coat.

Use the Free Calculator

Why You Need This Calculation

  • Estimating paint correctly saves money and avoids color-mismatch issues from buying extra batches later.

Common Mistakes

Forgetting to account for two coats.

Most paint jobs require two coats; double your estimate.

Not subtracting doors and windows.

Each door saves about 21 sq ft, each window about 15 sq ft.

Using ceiling coverage rate for textured walls.

Textured surfaces absorb more paint; reduce coverage to 300 sq ft/gal.

Frequently Asked Questions