# Paint calculator

Canonical interactive tool: https://taskpencil.com/tools/paint-calculator/

Estimate wall and optional ceiling paint from room dimensions, openings, coverage, and coats.

## Instructions

1. Enter your values in the labeled fields.

2. Results update automatically as inputs change. Review the result and assumptions.

3. Copy or print your result.

## Formula and example

Wall area = 2 × (length + width) × height. Subtract door and window areas and optionally add length × width for the ceiling. Gallons = paintable area × coats ÷ label coverage × (1 + extra allowance / 100). A 12 × 10 × 8 ft room with one 21 sq ft door and two 15 sq ft windows has 301 sq ft of walls; two coats at 350 sq ft/gallon plus 10% extra need 1.892 gallons, rounded up to two 1-gallon cans.

## Limits

Rectangular rooms, feet, square feet, and US gallons only. Default door/window areas and 350 sq ft coverage are editable assumptions. Follow the paint label for actual coverage. Excludes primer, trim, surface preparation, and unusual shapes. Openings cannot exceed wall area. All processing is local; inputs are not stored or transmitted.