Paint Calculator

How to Use This Calculator

1. Enter your room length and width in feet using a tape measure for accuracy
2. Enter the wall height (typically 8 feet for standard rooms, 9-10 feet for newer construction)
3. Specify the number of coats you plan to apply (2 coats is recommended for most projects)
4. Enter the number of doors and windows to subtract from the paintable area
5. Click "Calculate Paint" to see exactly how many gallons you need

What is a Paint Calculator?

A paint calculator is an essential tool for homeowners, contractors, and DIY enthusiasts that estimates how much paint is needed to cover walls based on room dimensions. The calculator determines your total wall surface area by measuring the room perimeter and multiplying it by the ceiling height. It then subtracts non-paintable surfaces such as doors and windows, and factors in the number of coats to give you an accurate gallon estimate.

Using a paint calculator before visiting the hardware store prevents two common problems: buying too little paint and needing to make another trip mid-project, or buying too much and wasting money on paint that will dry out before you can use it. An accurate estimate ensures color consistency throughout your room since paint from the same batch will match perfectly.

Paint Coverage Guidelines

Understanding paint coverage helps you plan your project more effectively:

• Standard coverage: One gallon of quality interior paint covers approximately 350-400 square feet per coat on smooth, primed walls
• Textured walls: Textured surfaces like knockdown, orange peel, or popcorn ceilings may require up to 25% more paint due to increased surface area
• Dark to light colors: Painting over dark colors with a lighter shade often requires 3 or more coats for complete coverage. Consider using a tinted primer first
• New drywall: Unpainted drywall is porous and absorbs more paint. Always apply primer first, or use a paint-and-primer combination
• Previously painted walls: If the existing paint is in good condition and you're applying a similar color, two coats typically provide excellent coverage

Choosing the Right Paint Type

Different rooms and surfaces require different paint finishes:

• Flat/Matte: Best for ceilings and low-traffic areas. Hides imperfections but difficult to clean
• Eggshell: Slight sheen, good for living rooms and bedrooms. Easy to clean and hides minor flaws
• Satin: Smooth finish ideal for kitchens, bathrooms, and hallways. Resists moisture and cleans easily
• Semi-gloss: Durable and moisture-resistant. Perfect for trim, doors, cabinets, and high-humidity areas
• High-gloss: Maximum durability and shine. Used for trim and doors where a dramatic finish is desired

Calculation Formula

The calculator uses these industry-standard formulas:

Wall Area = 2 x (Length + Width) x Height

Paintable Area = Wall Area - (Doors x 20 sq ft) - (Windows x 15 sq ft)

Gallons Needed = (Paintable Area x Coats) / 350

The 350 square feet per gallon figure is a conservative industry average that accounts for typical wall conditions and application methods.

Pro Tips for Better Results

• Always buy slightly more paint than calculated to account for touch-ups and future repairs
• Keep the paint can label or have the store save your custom color formula for future reference
• Calculate ceiling paint separately if painting overhead surfaces
• For accent walls, measure that wall individually rather than using room dimensions
• High-quality paint provides better coverage and durability, often requiring fewer coats than budget options