Complete Guide to Paint Coverage Calculator

This guide will help you accurately calculate paint requirements for any painting project, whether interior or exterior. Understanding paint coverage, waste factors, and application techniques is essential for successful results.

Understanding Paint Coverage

Paint coverage varies significantly by paint type and quality:

• Latex paints: Typically 8-12 m²/L (320-480 ft²/gal)
• Oil-based paints: Usually 6-10 m²/L (240-400 ft²/gal)
• Premium paints: Can achieve 10-14 m²/L (400-560 ft²/gal)
• Budget paints: May only cover 6-9 m²/L (240-360 ft²/gal)

Always check the paint can label for exact coverage rates, as formulations vary by manufacturer.

Calculating Wall Area

The basic formula for paintable area is:

Paintable Area = (Perimeter × Height) - Openings

Measuring Perimeter

For rectangular rooms: Perimeter = 2 × (Length + Width)

For irregular rooms, measure each wall segment separately and sum them. Typical residential rooms have perimeters of 12-30m (40-100ft).

Accounting for Openings

Standard opening sizes:

• Single door: ~2.0 m² (21 ft²)
• Single window: 1.5-2.5 m² (16-27 ft²)
• Double window: 3-4 m² (32-43 ft²)

Sum all openings and subtract from total wall area. Openings typically account for 10-20% of wall area.

Number of Coats

Most projects require multiple coats:

• Interior walls: 2 coats minimum for even coverage
• Color changes: 3 coats, especially dark to light
• Exterior surfaces: 2-3 coats depending on substrate condition
• Primer: Counts as separate coat if using different product

Special Considerations

Textured Surfaces

Textured walls (popcorn, stucco, heavy texture) require 20-30% more paint than smooth walls. Add this percentage to your calculated volume.

Exterior vs Interior

Exterior paints are typically thicker and may cover slightly less (8-10 m²/L) than interior paints (10-12 m²/L), but formulations vary.

Trim and Doors

Calculate trim and doors separately:

• Measure linear feet/meters of trim
• Doors are usually 2-3 m² each
• Trim typically uses semi-gloss or gloss paint with 10-12 m²/L coverage

Best Practices

• Buy 10-15% extra for touch-ups and future repairs
• Store leftovers in sealed containers labeled with room and color code
• Mix multiple cans together (boxing) for consistency if using more than one container
• Keep paint from same batch for color consistency

Common Mistakes

• Forgetting to subtract openings: Can lead to 10-20% over-ordering
• Underestimating coats: One coat is rarely sufficient
• Using wrong coverage rate: Always check paint can label
• Not accounting for texture: Textured surfaces need 20-30% more paint

Conclusion

Accurate paint calculations save time and money. Use this calculator as your starting point, verify coverage rates on your paint cans, and always order extra for touch-ups and future repairs.