Paint Calculator โ Estimate Gallons of Paint for Any Room
Calculate how many gallons of paint you need for a room. Enter wall dimensions; doors; and windows for an accurate estimate.
Buying the right amount of paint means fewer store trips and less waste. One gallon typically covers 350-400 square feet on smooth surfaces. This calculator deducts doors and windows automatically.
How many gallons of paint for a 12x12 room?
A 12x12 room with 8-foot ceilings has about 384 sq ft of wall area. After deducting a door and two windows; you need about 1 gallon per coat or 2 gallons for two coats.
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How This Material Calculator Works
This calculator uses industry-standard formulas to estimate the quantity of materials needed for your project. It factors in standard waste allowances (typically 5-10% depending on material type) so you purchase enough without significant overbuying. Measurements are based on common product dimensions available at major retailers and building supply stores. For best results, measure your project area carefully and round up to the nearest whole unit when purchasing.
Tips for Accurate Material Estimates
Always measure twice before ordering materials. Account for cuts, corners, and irregular shapes by adding 10% extra for most materials. For concrete and masonry, consider the subgrade preparation and drainage requirements. Check local building codes before starting any project โ permits may be required for structural work, fencing over certain heights, or decks above ground level. Buy materials from the same batch to ensure color consistency, especially for tiles, pavers, and paint.
Key Information
| Parameter | Details |
|---|---|
| Coverage per Gallon | 350-400 sq ft (one coat) |
| Standard Door Deduction | 21 sq ft per door |
| Standard Window Deduction | 15 sq ft per window |
| Coats Recommended | 2 coats for best coverage |
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Use Calculator NowFrequently Asked Questions
How many gallons of paint for a 12x12 room?
A 12x12 room with 8-foot ceilings has about 384 sq ft of wall area. After deducting a door and two windows; you need about 1 gallon per coat or 2 gallons for two coats.
Do I need primer before painting?
Primer is recommended when painting over dark colors; new drywall; stains; or when switching between oil and latex paint. Self-priming paints work for minor color changes on already-painted walls.
How much does a gallon of paint cover?
Most interior paints cover 350-400 sq ft per gallon on smooth surfaces. Rough or textured surfaces may only get 250-300 sq ft coverage. Always check the manufacturer label.
How much extra material should I order?
For most construction materials, order 10% extra to account for cuts, waste, breakage, and mistakes. For tiles and pavers, add 15% if using a diagonal or herringbone pattern. Concrete should include a 5-10% overage since running short mid-pour is costly. Always keep leftover materials for future repairs.
Do I need a permit for my project?
Permit requirements vary by location and project scope. Generally, structural work (walls, roofing, foundations), electrical, plumbing, fences over 6 feet, and decks above 30 inches require permits. Cosmetic work like painting, flooring, and landscaping usually does not. Check with your local building department before starting.
How do I convert between material units?
Common conversions: 1 cubic yard = 27 cubic feet. 1 square (roofing) = 100 sq ft. 1 board foot = 1 inch ร 12 inches ร 12 inches of lumber. Concrete is sold in cubic yards; multiply length ร width ร depth in feet and divide by 27. Our calculator handles these conversions automatically.
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Last updated: March 2026