How Much Paint Do I Need? Room Calculator & Coverage Guide

Whether you're refreshing a single room or painting your entire home, calculating the right amount of paint prevents frustrating trips back to the store and wasted money on unused gallons. Our paint calculator makes this simple, accounting for doors, windows, and multiple coats.

The standard paint coverage rate is 350-400 square feet per gallon, but this varies based on surface texture, paint quality, and application method. This guide will help you calculate precisely what you need.

Paint Coverage Rates

One gallon of paint typically covers:

• Smooth drywall: 400 sq ft per gallon
• Textured walls: 300 sq ft per gallon
• New drywall (primed): 350 sq ft per gallon
• Bare wood: 350 sq ft per gallon
• Brick or stucco: 150-200 sq ft per gallon

For calculations, we use 350 sq ft as a conservative estimate.

Calculating Wall Area

Wall Area = (Room Perimeter × Height) - Doors - Windows

For a 12×14 foot room with 8-foot ceilings:

• Perimeter: (12 + 14) × 2 = 52 feet
• Wall area: 52 × 8 = 416 sq ft
• Minus 2 windows (15 sq ft each): 416 - 30 = 386 sq ft
• Minus 1 door (20 sq ft): 386 - 20 = 366 sq ft
• For 2 coats: 366 × 2 = 732 sq ft total coverage needed
• Gallons: 732 ÷ 350 = 2.1 gallons

Standard Deductions

• Standard door: 20 sq ft
• Standard window: 15 sq ft
• Large window: 25 sq ft
• Sliding door: 40 sq ft

How Many Coats Do You Need?

• 1 coat: Same color refresh
• 2 coats: Standard for most color changes
• 3 coats: Covering dark colors with light, or using deep/bright colors
• Primer + 2 coats: New drywall, stain blocking, or drastic color changes

Frequently Asked Questions

How many gallons for a 12x12 room?

A 12x12 room with 8-foot ceilings has about 384 sq ft of wall space. After deducting for one door and one window, you need approximately 2 gallons for two coats.

Should I buy extra paint?

Yes, buy 10% extra for touch-ups and future repairs. Store the extra paint properly and label it with the room and date.

Is one coat ever enough?

One coat works when repainting with the same or very similar color over a well-prepared surface. For most projects, two coats provide better coverage and durability.