How do I calculate how much paint I need?

Measure the length and height of each wall you're painting. Multiply length × height for each wall to get square feet. Add all walls together, subtract door and window openings, then divide by the paint's coverage rate (typically 350-400 sq ft per gallon for interior latex).

How many coats of paint do I need?

Most interior painting requires 2 coats for best coverage and color, especially over light or unprimed surfaces. One coat may be sufficient for touch-ups or repainting the same color. New drywall, bold color changes, and exterior surfaces typically need 2 coats.

How much does paint cost?

Standard Interior Latex costs $25-40/gallon, Premium Interior Latex costs $40-60/gallon, Exterior Latex costs $30-50/gallon, Primer costs $20-35/gallon, and Cabinet/Trim Paint costs $40-70/gallon. Higher quality paints often provide better coverage and durability.

Paint Calculator — How Much Paint Do I Need?

Calculate Your Paint Needs

Room Length

Width of the room

Room Width

Depth of the room

Ceiling Height

Standard interior is 8-9 feet

Number of Doors

Standard door = 21 sq ft each

Number of Windows

Standard window = 15 sq ft each

Additional Area to Deduct

sq ft

For custom openings or areas you don't want to paint

Number of Coats

2 coats provides the best finish for most projects

Paint Type

Surface Texture

Textured surfaces require more paint for full coverage

How to Calculate Paint Coverage

Calculating the right amount of paint needed for your project is essential to avoid waste and unnecessary store trips. Our paint calculator makes this process simple by automating the math based on your room dimensions and paint type.

Simple Formula for Paint Needed

Wall Area (sq ft) - Openings (doors/windows) ÷ Coverage Rate × Number of Coats = Gallons Needed

Step-by-Step Calculation

Measure your walls: Calculate the length and height of each wall you're painting
Find total wall area: Multiply length × height for each wall, then add them together
Subtract openings: Deduct area for doors (21 sq ft standard), windows (15 sq ft standard), and other areas not being painted
Check paint coverage: Find the square footage coverage on your paint can (typically 350-400 sq ft per gallon for interior)
Account for coats: Multiply by the number of coats needed (usually 2 for best results)
Round up: Always round up to the nearest gallon to ensure complete coverage

Paint Types & Coverage Guide

Different paint types have different coverage rates and costs. Understanding these differences helps you choose the right paint for your project and calculate needs accurately.

Paint Type	Best For	Coverage Rate	Price Range
Standard Interior Latex	Interior walls, touch-ups, budget projects	350-400 sq ft/gal	$25-40/gal
Premium Interior Latex	Interior walls, living spaces, superior finish	350-400 sq ft/gal	$40-60/gal
Exterior Latex	Siding, trim, fences, exterior surfaces	250-350 sq ft/gal	$30-50/gal
Primer	New drywall, stains, color changes, repairs	200-300 sq ft/gal	$20-35/gal
Cabinet/Trim Paint	Doors, trim, cabinets, detailed work	250-350 sq ft/gal	$40-70/gal

Interior vs. Exterior Paint

Interior and exterior paints are formulated differently to handle their specific environments. Understanding these differences helps you choose the right product and calculate coverage accurately.

Interior Paint

Best uses: Bedrooms, living rooms, kitchens, bathrooms, and other indoor spaces. Interior latex paints offer excellent color variety, low odor, and easy cleanup with water.

Better finish quality and durability indoors
Lower VOC (volatile organic compounds) for better indoor air quality
Wider color selection available
Coverage: 350-400 sq ft per gallon

Exterior Paint

Best uses: Siding, trim, fences, decks, and outdoor surfaces. Exterior paint is formulated to withstand weather, UV rays, and moisture.

Enhanced weather and UV resistance
Better adhesion to exterior surfaces
Mildew and moisture protection
Coverage: 250-350 sq ft per gallon (typically less than interior due to texture)

Paint Primer Guide

Primer is the foundation for a successful paint job. It improves adhesion, coverage, and durability of your topcoat paint.

When to Use Primer

New drywall: Must prime before painting to achieve even color and proper coverage
Dark to light color changes: Primer reduces the number of topcoats needed
Stains and water damage: Primer blocks stains from bleeding through
New surfaces: Bare wood, metal, or masonry benefit from primer
Glossy surfaces: Sand and prime glossy surfaces before painting

Primer Coverage

Primers typically cover 200-300 square feet per gallon. Calculate primer the same way as paint, but use the primer's specific coverage rate. Most projects require one coat of primer before two coats of topcoat paint.

Paint Buying & Application Tips

Always Buy Extra

Buy an extra gallon or quart for future touch-ups. Paint color may vary between batches, so having extra ensures consistent touch-ups years later.

Account for Surface Texture

Textured or rough surfaces require 10-20% more paint for full coverage. New drywall and primer requirements can increase your overall needs.

Quality Matters

Premium paints often provide better coverage, durability, and finish quality. While they cost more per gallon, you may use fewer coats, saving money overall.

Two Coats Recommended

While one coat may look complete, two coats provide better color depth, coverage, and longevity. Plan on two coats for most projects.

Test Before Buying

Paint color appears different on large walls than on tiny samples. Obtain sample sizes and test on your walls before committing to full quantities.

Store Paint Properly

Store unused paint in a cool, dry place with the lid sealed tight. Properly stored paint can last several years for future touch-ups.

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