Paint Coverage Calculator

The Formula

Paint coverage is calculated based on net paintable area (walls minus doors and windows), number of coats, and a standard coverage rate of 350 sq ft per gallon.

Variable Definitions

How to Use This Calculator

1. 1

   Enter your room dimensions (length, width, ceiling height).

2. 2

   Enter the number of doors and windows to subtract from the wall area.

3. 3

   Select the number of coats (2 is standard for full coverage).

4. 4

   The result includes a 10% waste buffer — always round up to the nearest gallon.

5. 5

   Consider paint sheen: flat hides imperfections but is harder to clean; eggshell/satin are best for living areas; semi-gloss is ideal for kitchens, bathrooms, and trim.

Common Applications

• Estimating how many gallons of paint to buy for a room painting project to avoid multiple trips to the store
• Planning paint budget for repainting a house interior, accounting for the number of coats and door or window deductions
• Comparing paint quantities needed for different sheens and surface textures that affect coverage rates

Paint coverage — one gallon covers roughly 350 sq ft per coat

Understanding the Concept

Paint coverage varies by surface texture, paint quality, and application method. Smooth drywall allows the standard 350 sq ft/gallon coverage. Rough textures, brick, or bare drywall absorb more paint and may require 300 sq ft/gallon or even a primer coat. When in doubt, buy one extra quart. Leftover paint stores well sealed for touch-ups. Paint sheen also affects coverage and durability: flat paint hides imperfections best but is hard to clean, while semi-gloss and high-gloss are more durable and washable but reveal surface flaws more easily. For living rooms and bedrooms, eggshell or satin finishes offer a good balance. For kitchens, bathrooms, and trim, semi-gloss is recommended for its moisture resistance and cleanability. Proper surface preparation is just as important as the paint itself: cleaning walls, patching holes, sanding rough spots, and applying quality painter's tape all contribute to a professional-looking result that lasts longer and requires fewer coats.

Frequently Asked Questions

Sources & References