Paint Calculator - Calculate Paint Coverage & Quantity
Calculate the exact amount of paint needed for your walls, rooms, and surfaces. Get accurate estimates with waste factor calculations, cost analysis, and coverage recommendations.
Paint Coverage Calculator
Paint Calculation Results
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Calculation Steps
- Calculate Wall Area: Total wall area = (Length + Width) × 2 × Height
- Subtract Openings: Deduct area of doors (21 sq ft each) and windows (12 sq ft each)
- Apply Coats: Multiply paintable area by number of coats
- Add Waste Factor: Add percentage for touch-ups and application loss
- Calculate Gallons: Divide total area by paint coverage rate
- Round Up: Always round up to nearest quarter gallon for purchasing
About This Paint Calculator
Our professional paint calculator helps you determine the exact amount of paint needed for any interior or exterior painting project. Whether you're painting a single room or an entire house, this tool provides accurate estimates that account for multiple coats, waste factors, and opening deductions.
The calculator uses industry-standard formulas and considers various factors that affect paint consumption, including surface texture, paint type, and application method. This ensures you purchase the right amount of paint without waste or shortage.
Key Features:
- Accurate coverage calculations for rooms and surfaces
- Multiple coat support with automatic calculations
- Door and window deduction for precise estimates
- Customizable waste factors for different project types
- Cost estimation with paint price input
- Support for different paint types and finishes
- Surface type considerations for better accuracy
How to Use the Paint Calculator
Step 1: Measure Your Room
Measure the length, width, and height of your room in feet. For irregular rooms, break them into rectangular sections and calculate each separately.
Step 2: Count Openings
Count the number of doors and windows. The calculator uses standard sizes (doors: 7×3 ft, windows: 3×4 ft) but you can adjust for custom sizes.
Step 3: Select Paint Specifications
Choose your paint coverage rate (check the paint can label), number of coats needed, and appropriate waste factor for your project complexity.
Step 4: Advanced Options (Optional)
Set paint price for cost estimation, select paint type and finish, and specify surface type for more accurate calculations.
Step 5: Calculate and Review
Click "Calculate Paint Needed" to get your results. Review the detailed breakdown and adjust inputs if necessary.
Paint Calculation Formula
Net Area = Wall Area - (Doors × 21) - (Windows × 12)
Total Area = Net Area × Number of Coats
Area with Waste = Total Area × (1 + Waste Factor/100)
Paint Needed = Area with Waste ÷ Coverage Rate
Standard Measurements:
- Standard Door: 7 feet × 3 feet = 21 square feet
- Standard Window: 3 feet × 4 feet = 12 square feet
- Typical Coverage: 350-400 square feet per gallon
- Recommended Waste Factor: 10-15% for most projects
Coverage Variations by Surface:
- Smooth Drywall: 400 sq ft per gallon
- Textured Surfaces: 350 sq ft per gallon
- Rough Surfaces: 300 sq ft per gallon
- Primer Application: 200-250 sq ft per gallon
Use Cases & Applications
Residential Projects
- Interior room painting
- Whole house renovations
- Bedroom and living space updates
- Kitchen and bathroom painting
- Ceiling painting projects
Commercial Applications
- Office space renovations
- Retail store painting
- Restaurant interior updates
- Warehouse painting projects
- Institutional facilities
Professional Use
- Contractor estimations
- Project bidding
- Material ordering
- Cost analysis
- Client consultations
DIY Projects
- Home improvement planning
- Paint store visits
- Budget estimation
- Project timeline planning
- Color scheme planning
Calculation Examples
Example 1: Standard Bedroom
Room: 12' × 10' × 8' with 1 door and 2 windows
Calculation: Wall Area = (12+10) × 2 × 8 = 352 sq ft
Minus Openings: 352 - 21 - 24 = 307 sq ft
Two Coats: 307 × 2 = 614 sq ft
With 10% Waste: 614 × 1.1 = 675 sq ft
Paint Needed: 675 ÷ 350 = 1.9 gallons (2 gallons recommended)
Example 2: Living Room
Room: 20' × 15' × 9' with 2 doors and 4 windows
Calculation: Wall Area = (20+15) × 2 × 9 = 630 sq ft
Minus Openings: 630 - 42 - 48 = 540 sq ft
Two Coats: 540 × 2 = 1,080 sq ft
With 15% Waste: 1,080 × 1.15 = 1,242 sq ft
Paint Needed: 1,242 ÷ 350 = 3.5 gallons (4 gallons recommended)
Example 3: Kitchen
Room: 14' × 12' × 8' with 2 doors and 3 windows
Calculation: Wall Area = (14+12) × 2 × 8 = 416 sq ft
Minus Openings: 416 - 42 - 36 = 338 sq ft
Two Coats: 338 × 2 = 676 sq ft
With 10% Waste: 676 × 1.1 = 744 sq ft
Paint Needed: 744 ÷ 350 = 2.1 gallons (2.5 gallons recommended)
Frequently Asked Questions
How much paint do I need for a 12x12 room?
For a 12x12 room with 8-foot ceilings, you'll need approximately 2-3 gallons of paint for two coats. This assumes standard doors and windows and accounts for a 10% waste factor.
How do you calculate paint coverage?
Paint coverage is calculated by determining the total wall area, subtracting openings like doors and windows, multiplying by the number of coats, adding a waste factor, then dividing by the paint's coverage rate (typically 350-400 sq ft per gallon).
Should I round up when buying paint?
Yes, always round up to the nearest quarter or half gallon. It's better to have slightly more paint for touch-ups than to run short during the project. Most paint stores also offer better prices on full gallon purchases.
What's a good waste factor percentage?
A 10% waste factor is standard for most projects. Use 5% for professional applications, 15% for complex surfaces with many cuts and angles, and 20% for very rough or highly textured surfaces.
Does paint type affect coverage?
Yes, different paint types have different coverage rates. Primer typically covers 200-250 sq ft per gallon, while quality latex paints cover 350-400 sq ft per gallon. Oil-based paints may have slightly different coverage rates.
How many coats of paint do I need?
Most painting projects require two coats for optimal coverage and color depth. You may need three coats when making dramatic color changes (dark to light) or when using certain paint finishes.
Should I include the ceiling in my calculation?
This calculator focuses on wall surfaces. For ceilings, calculate separately: ceiling area = length × width. Ceiling paint often has different coverage rates and may require different paint types.
What if my room has custom-sized doors or windows?
The calculator uses standard sizes (doors: 21 sq ft, windows: 12 sq ft). For custom sizes, measure your actual openings and adjust the waste factor accordingly, or calculate the net paintable area manually.