Room Paint Quantity Calculator (Advanced)

How This Tool Works

This advanced paint calculator accounts for all factors that affect paint quantity: room dimensions, windows, doors, ceiling, paint type, and number of coats. It automatically subtracts window and door areas from the total wall area, so you get an accurate estimate of the actual paintable surface.

The calculator uses industry-standard coverage rates that vary by paint finish type. Flat paint provides the best coverage (10 m² per liter), while gloss paint provides less coverage (6 m² per liter) because it contains more binders and less pigment. The tool includes a 10% waste factor for touch-ups, coverage variations, and application method differences.

Paint Coverage by Type

• Flat/Matte: 10 m² per liter - best coverage, hides imperfections
• Eggshell: 9 m² per liter - good coverage, slight sheen
• Satin: 8 m² per liter - moderate coverage, smooth finish
• Semi-Gloss: 7 m² per liter - lower coverage, durable, easy to clean
• Gloss: 6 m² per liter - lowest coverage, very durable, high shine
• Note: Coverage varies by brand - always check paint can labels

Tips for Accurate Calculations

• Measure Accurately: Use a tape measure for precise room dimensions
• Account for All Surfaces: Don't forget baseboards, trim, and built-ins if painting them
• Consider Color Changes: Dark to light or light to dark may need extra coats
• Buy All at Once: Purchase all paint needed at once for color consistency
• Check Paint Labels: Actual coverage rates vary by brand and formula
• Plan for Waste: The 10% waste factor accounts for normal variations
• Test Coverage: Paint a small test area to verify coverage before full project

FAQ

• How do I calculate paint for a room with windows and doors?
  Measure room length, width, and ceiling height. Calculate total wall area: 2 × (length × height) + 2 × (width × height). Subtract window area (~1.5 m² each) and door area (~2 m² each). Add ceiling area if painting it. Divide by paint coverage rate (varies by paint type) and multiply by number of coats. Add 10% for waste.
• How much paint do I need for a 4m × 3m room?
  For a 4m × 3m room with 2.5m ceiling height: Wall area = 2×(4×2.5) + 2×(3×2.5) = 35 m². Subtract 1 window (1.5 m²) and 1 door (2 m²) = 31.5 m². With flat paint (10 m²/L) and 2 coats: (31.5/10) × 2 × 1.1 = ~7 liters. Add primer if needed.
• Should I include the ceiling in my paint calculation?
  Yes, if you plan to paint the ceiling. Ceiling area = length × width. Add this to your total area calculation. Ceilings typically use flat paint for best coverage. Most rooms need 1-2 coats for ceilings depending on color change.
• How do windows and doors affect paint quantity?
  Windows and doors reduce the area you need to paint. Average window area is ~1.5 m², average door is ~2 m². The calculator automatically subtracts these areas from your total wall area. If you have unusually large windows or doors, you may want to measure them individually.
• How many coats of paint do I need?
  Most rooms need 2 coats for proper coverage, color depth, and durability. One coat may work for: touching up the same color, very high-quality paint on well-prepared surfaces, or minor color changes. Two coats are recommended for new paint jobs and color changes. The calculator multiplies by your selected number of coats.
• Do I need primer?
  Primer is recommended for: new drywall or plaster, unpainted surfaces, dramatic color changes (especially dark to light), stained or damaged surfaces. Primer typically covers 10-12 m² per liter, similar to flat paint. The calculator provides primer estimates for one coat.