About Paint Calculator

Calculate how much paint to buy for one or more rooms. Enter room dimensions (length, width, height), number of doors and windows, and whether to include the ceiling. The tool subtracts door area (20 sq ft each) and window area (15 sq ft each) from total wall surface, multiplies by your chosen coat count, and divides by paint coverage to determine gallons needed. A cost estimator adds 15% for supplies (tape, rollers, drop cloths) on top of paint cost.

• Room calculator with per-room dimensions, doors, windows, and optional ceiling
• Area calculator mode for direct square footage input
• Five paint coverage presets: premium (400 sq ft/gal), standard (350), budget (300), primer (275), textured (250)
• 1–3 coats with per-room gallon breakdown
• Cost estimate includes paint price per gallon plus 15% supply surcharge
• Purchase recommendation based on gallon count (e.g., “Buy 2 gallons”)
• Calculation history with CSV export for multi-project tracking

Frequently Asked Questions

Why does the tool subtract 20 sq ft per door and 15 sq ft per window?

Those are standard estimates for a typical interior door (3×6.5 ft ≈ 20 sq ft) and a medium window (3×5 ft = 15 sq ft). If your doors or windows are significantly larger or smaller, adjust the count to compensate.

Should I select 1 or 2 coats?

Two coats is almost always the right answer. One coat rarely provides full, even coverage—especially when changing colors or painting over patches. The tool defaults to 2 coats for this reason.