Paint Calculator

Paint Calculator

Estimate wall area, paint gallons and a practical purchase amount.

UNDERSTAND THE ANSWER

How is this calculated?

The estimate subtracts 20 sq ft per door and 15 sq ft per window, then assumes one gallon covers about 350 sq ft per coat.

Wall paint estimatePaintable area = Perimeter × Height − Doors − Windows

A practical example

A 14 × 12 ft room with 8 ft walls, two doors, two windows and two coats needs about 2.2 gallons, so buying 3 gallons is practical.

Assumptions, interpretation and common mistakes

Calculation assumptions

  • The room is rectangular with a constant wall height.
  • Each door removes 20 sq ft and each window removes 15 sq ft.
  • One gallon covers 350 sq ft per coat before a 10% purchase buffer.

How to interpret the result

  • Recommended purchase rounds up to whole gallons.
  • Paintable area excludes estimated door and window openings.
  • Coverage for all coats multiplies net wall area by the coat count.

Common mistakes to avoid

  • Using floor area instead of wall perimeter and height.
  • Assuming manufacturer coverage is identical on textured or porous surfaces.
  • Forgetting primer, ceiling, trim or major color changes.