Paint Calculator - Calculate Exact Gallons Needed
Calculate exact paint gallons & cost for walls, ceilings & trim. Free paint coverage calculator with primer & waste calculations. Save time and money on your painting project!
Paint Requirements
How to Use the Paint Calculator
Our free paint calculator helps you determine exactly how much paint you need for any room or surface. Whether you're painting walls, ceilings, or trim, get accurate gallon estimates and cost projections to avoid over-buying or making multiple trips to the store.
Step-by-Step Instructions:
- Measure Your Room: Measure the length and width of each wall in feet. For ceilings, measure length and width. For irregular rooms, break them into sections and calculate separately.
- Calculate Total Square Footage: The calculator automatically computes total paintable area by adding all surfaces (walls, ceiling, trim) you plan to paint.
- Subtract Openings: Enter the number and size of doors and windows to exclude them from the total area. This ensures accurate paint quantities.
- Choose Paint Type: Select between standard paint (covers 350-400 sq ft per gallon) or premium paint (covers 400-450 sq ft per gallon). Premium paints often require fewer coats.
- Number of Coats: Most walls need 2 coats. Dark colors or porous surfaces may need 3 coats. Add primer if painting over dark colors or bare drywall.
- Add Waste Factor: Include 10-15% extra paint for touch-ups, uneven surfaces, and mistakes. This is especially important for textured walls.
- Enter Paint Price: Input the cost per gallon to get total project cost estimate. Include primer cost if needed.
Pro Tip:
One gallon of paint typically covers 350-400 square feet with one coat. However, actual coverage varies by paint quality, surface texture, and application method. Always buy slightly more than calculated to ensure color consistency within the same batch.
Paint Coverage Guide
Standard Paint Coverage Rates
| Paint Type | Coverage per Gallon | Typical Use |
|---|---|---|
| Standard Interior Paint | 350-400 sq ft | Most walls and ceilings |
| Premium Interior Paint | 400-450 sq ft | One-coat coverage, high-quality finish |
| Primer | 300-350 sq ft | Bare drywall, dark-to-light transitions |
| Exterior Paint | 250-350 sq ft | Siding, stucco, brick |
| Ceiling Paint | 350-400 sq ft | Flat white ceiling paint |
Factors That Affect Paint Coverage
- Surface Texture: Rough, porous, or textured surfaces absorb more paint and require 10-25% more coverage than smooth surfaces.
- Paint Quality: Premium paints have higher pigment concentration and better coverage, often eliminating the need for a third coat.
- Color Change: Painting light over dark (or vice versa) requires extra coats. Use tinted primer to reduce topcoat needs.
- Application Method: Spraying uses 20-30% more paint than rolling. Brushing is most economical but slowest.
- Previous Surface Condition: New drywall absorbs more paint than previously painted walls. Always prime bare drywall first.
Cost Estimation Tips
Paint costs vary widely based on quality and brand. Here's a breakdown to help you budget your project:
Budget Paint
$15-25/gal
- • Basic coverage
- • 2-3 coats needed
- • Good for low-traffic areas
- • Rental properties
Mid-Range Paint
Popular$30-50/gal
- • Good coverage
- • 2 coats typical
- • Durable finish
- • Best value for money
Premium Paint
$50-80/gal
- • Excellent coverage
- • 1-2 coats only
- • Superior durability
- • High-traffic areas
Money-Saving Tip:
While premium paint costs more upfront, it often covers better and lasts longer, potentially saving money overall. One coat of premium paint may cost less than two coats of budget paint when you factor in labor time and materials.
Common Paint Calculation Mistakes to Avoid
❌ Not Accounting for Doors and Windows
Many people calculate total wall area but forget to subtract doors and windows. A standard door is 21 sq ft, and a window averages 15-20 sq ft. This can lead to over-purchasing by 1-2 gallons.
❌ Forgetting About Waste and Touch-Ups
Always add 10-15% extra for waste, spills, and future touch-ups. Paint from different batches may not match perfectly, so having extra from your original batch is crucial.
❌ Ignoring Surface Texture
Textured walls, stucco, or brick can use 20-30% more paint than smooth drywall. If you're painting a textured surface, increase your coverage factor accordingly.
❌ Not Considering Color Changes
Painting a light color over dark (or dark over light) requires extra coats. Use a tinted primer to save on topcoats and improve final color accuracy.
❌ Buying Cheap Paint to Save Money
Budget paint often requires 3 coats compared to 2 coats for quality paint. When you factor in labor time and extra materials, premium paint can actually be more economical.
Frequently Asked Questions
How much paint do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings has approximately 384 square feet of wall space (not including ceiling). After subtracting a door and window, you'll need about 1 gallon for one coat, or 2 gallons for two coats. Add the ceiling (144 sq ft) and you'll need an additional gallon.
Do I need primer before painting?
Yes, use primer when: painting new drywall, covering dark colors with lighter paint, painting over glossy surfaces, dealing with stains or water damage, or when paint instructions recommend it. Primer improves adhesion and coverage, potentially saving you a topcoat.
How many coats of paint should I apply?
Most walls need 2 coats for proper coverage and color saturation. Dark colors, dramatic color changes, or porous surfaces may require 3 coats. Premium "one-coat" paints can cover in fewer coats but cost more per gallon.
How long does a gallon of paint last?
One gallon covers 350-400 square feet per coat with standard paint. For a typical bedroom (12x12), one gallon does one coat on all walls. Unopened paint lasts 10+ years; opened paint lasts 2-5 years if properly sealed and stored.
Should I buy paint in gallons or quarts?
Gallons are more economical for rooms. Quarts work well for small spaces, touch-ups, or testing colors. One gallon equals four quarts but costs less than buying four quarts separately. Always buy from the same batch to ensure color consistency.
What's the difference between paint and primer?
Primer is designed to seal surfaces, improve adhesion, and provide a uniform base. Paint provides color and protection. Paint-and-primer combinations exist but may not perform as well as separate products for challenging surfaces or dramatic color changes.