Paint Calculator
Calculate how much paint you need for your project
How to Use This Calculator
Estimating paint for your room is simple with our calculator. Whether you are tackling a weekend DIY project or planning a full home makeover, accurate paint estimates help you budget correctly and avoid multiple trips to the store. Follow these steps to get an accurate estimate:
- Measure your room dimensions: Enter the length and width of your room in feet. Use a tape measure for accuracy. For irregularly shaped rooms, such as L-shaped spaces, measure and calculate each rectangular section separately, then add the results together.
- Enter wall height: Standard ceiling height is 8 feet, but enter your actual measurement for accuracy. Many newer homes have 9 or 10 foot ceilings, and older homes may have even higher ceilings.
- Count doors and windows: Enter the number of standard doors (typically 3 feet by 7 feet) and windows (approximately 3 feet by 5 feet). The calculator automatically subtracts their area from the total wall space using industry-standard dimensions.
- Select number of coats: Two coats is the industry standard for most painting projects and provides complete, even coverage. Choose one coat only for touch-ups or same-color refreshes. Select three coats when making dramatic color changes, such as painting light over dark or covering bold colors.
- Click calculate: View your comprehensive results showing total wall area, deductions for doors and windows, final paintable area, and the number of gallons needed.
The calculator uses the industry-standard coverage rate of 350 square feet per gallon, which accounts for typical wall textures, roller application methods, and minor waste. For textured walls or porous surfaces, consider adding 10-15% more paint to your purchase.
Understanding Paint Coverage
Understanding paint coverage rates is essential for accurate project planning. The industry standard is 350 to 400 square feet per gallon on smooth, previously painted surfaces. However, actual coverage varies significantly based on several important factors that every DIYer and professional painter should consider.
Coverage rates explained
Paint manufacturers test coverage under ideal laboratory conditions on smooth, primed surfaces. In real-world applications, you should expect the following coverage ranges: premium latex paint covers 350 to 400 square feet per gallon on smooth walls, while the same paint on textured surfaces covers only 250 to 300 square feet per gallon. Oil-based paints typically cover slightly less area, around 300 to 350 square feet per gallon. Always check the specific coverage rate listed on your paint can, as formulations vary by brand and product line.
Factors affecting coverage
Surface texture: Textured walls, popcorn ceilings, and knockdown finishes have more surface area and absorb more paint. Heavily textured surfaces can reduce coverage by 25-30% compared to smooth walls. Color change magnitude: Painting dark colors over light, or light over dark, dramatically affects how many coats you need. Going from navy blue to white might require a gray-tinted primer plus three topcoats. Paint quality: Premium paints contain more pigment and better resins, providing superior coverage and often requiring fewer coats than budget alternatives. Application method: Spraying typically uses 20-30% more paint than rolling due to overspray, while brushwork on trim uses paint efficiently but takes more time.
When primer is necessary
While paint-and-primer combinations work for many projects, separate primer is essential in certain situations. Use dedicated primer when painting new drywall (which is highly porous), bare wood, stained or smoke-damaged surfaces, or when making dramatic color changes. Shellac-based primers block stains and odors effectively. Bonding primers help paint adhere to glossy surfaces. PVA primers seal new drywall affordably. Investing in the right primer prevents adhesion problems and ensures your topcoat looks its best.
Sheen types and their uses
Paint sheen affects both appearance and durability. Flat or matte: No shine, excellent at hiding imperfections, but difficult to clean. Best for ceilings and low-traffic areas. Eggshell: Subtle soft sheen with moderate washability. Ideal for living rooms, dining rooms, and adult bedrooms. Satin: Noticeable sheen with good durability. Perfect for kitchens, bathrooms, kids' rooms, and hallways. Semi-gloss: Shiny and highly washable. Excellent for trim, doors, cabinets, and moisture-prone areas. Gloss: Maximum shine and durability. Used primarily for trim, furniture, and high-wear surfaces. Higher sheen levels are more durable but also highlight surface imperfections more noticeably.
Paint Project Examples
Example 1: Standard bedroom repaint
Jennifer wants to repaint her 12 by 14 foot master bedroom with 8 foot ceilings, changing from beige to a light gray. The room has one door and two windows. Using the calculator: wall perimeter is (12 + 14) x 2 = 52 feet, and wall area is 52 x 8 = 416 square feet. After subtracting one door (21 sq ft) and two windows (30 sq ft), she has 365 square feet of paintable area. With two coats for a moderate color change, she needs 730 square feet of coverage, or approximately 2.1 gallons. Jennifer purchases 3 gallons of satin finish paint, which gives her enough for complete coverage plus leftover for future touch-ups. Total project cost: approximately $120 for quality paint.
Example 2: Accent wall project
Michael wants to paint a single accent wall in his living room a bold navy blue. The wall measures 14 feet wide by 9 feet tall with no doors or windows. Wall area: 14 x 9 = 126 square feet. Because he is painting a deep, highly pigmented color, he plans for three coats despite the small area. Total coverage needed: 378 square feet. One gallon of paint is more than sufficient. However, dark colors like navy often require a gray primer for best results, so Michael also purchases one quart of tinted primer. The entire accent wall project requires less than one gallon of topcoat paint.
Example 3: Whole room with ceiling
Sarah is painting her entire 15 by 12 foot family room, including the ceiling. Walls: perimeter of 54 feet times 8 foot height equals 432 square feet, minus two doors (42 sq ft) and three windows (45 sq ft), leaving 345 square feet of wall area. Ceiling: 15 x 12 = 180 square feet. With two coats on walls (690 sq ft coverage) and one coat on the ceiling (180 sq ft coverage), she needs approximately 2 gallons of wall paint and 1 gallon of ceiling paint. Sarah budgets for 3 gallons of wall paint in eggshell finish and 1 gallon of flat ceiling paint. This comprehensive project transforms the entire room for under $200 in materials.
The calculation formula
Wall area: (Length + Width) x 2 x Height
Door deduction: 21 square feet per standard door (3 ft x 7 ft)
Window deduction: 15 square feet per standard window (3 ft x 5 ft)
Paintable area: Wall area - Door deductions - Window deductions
Paint needed: (Paintable area x Number of coats) / 350
This formula assumes standard door and window sizes. For larger openings like patio doors or picture windows, measure the actual dimensions and calculate the deduction manually.
Frequently Asked Questions
How much area does one gallon of paint cover?
One gallon of paint typically covers 350 to 400 square feet on smooth, previously painted surfaces with a single coat. However, this coverage rate assumes ideal conditions. Textured walls like knockdown or orange peel finishes absorb more paint, reducing coverage to 250-300 square feet per gallon. Porous surfaces such as new drywall, bare wood, or masonry may require even more paint. High-quality premium paints often achieve better coverage than budget options. Always check the manufacturer's specifications printed on the paint can for the most accurate coverage estimate for your specific product.
Do I need primer before painting my walls?
Primer is recommended in several specific situations but is not always necessary. You should use primer when painting over dark colors with a lighter shade, covering stains or water damage, painting new drywall for the first time, coating bare wood or unpainted surfaces, or painting over glossy finishes that paint will not adhere to well. Modern paint-and-primer-in-one products work adequately for repainting similar colors over surfaces in good condition. However, for challenging situations or dramatic color changes, a dedicated primer provides superior results and can actually save money by reducing the number of topcoats needed.
How many coats of paint do I need?
Two coats of paint is the industry standard for most interior painting projects and produces a uniform, professional-looking finish. One coat is sufficient only for minor touch-ups or refreshing the exact same color when the existing paint is in good condition. Three coats become necessary when making dramatic color changes, particularly when painting light colors over dark (such as white over navy) or when using highly pigmented colors like red, yellow, or deep orange that have poor natural coverage. When in doubt, plan for two coats, as a second coat ensures complete coverage and extends the life of your paint job.
How do I paint a dark room a light color?
Painting from dark to light is one of the most challenging color transitions. Start by cleaning walls thoroughly and repairing any imperfections. Apply a high-quality gray-tinted primer, which blocks dark colors more effectively than white primer. The gray creates a neutral base that prevents the dark color from showing through. Allow the primer to dry completely, typically 24 hours. Then apply two to three coats of your light-colored topcoat, allowing proper drying time between each coat. This process may seem time-consuming, but skipping the tinted primer often results in needing four or more topcoats, wasting both time and money.
How much paint do I need for a ceiling?
Calculating ceiling paint is straightforward: multiply the room length by the room width to find the square footage. For example, a 12 by 14 foot room has a 168 square foot ceiling. Divide this by the paint coverage rate (typically 350-400 square feet per gallon) to determine gallons needed. A standard bedroom ceiling usually requires less than one gallon. Ceiling paint is formulated with a thicker consistency to minimize drips and spatters. When repainting white over white, one coat often suffices. However, when covering stains, changing colors, or painting over a textured ceiling, plan for two coats and expect reduced coverage.
How much paint do I need for trim and doors?
Trim and door paint requirements are calculated separately from wall paint. A standard interior door (both sides) requires approximately one quart of paint. Window trim typically needs 1-2 quarts per window depending on complexity. Baseboards use about one quart per 100 linear feet. Crown molding requires similar quantities. For a typical bedroom with one door, two windows, and 40 feet of baseboard, plan on purchasing 2-3 quarts of trim paint. Semi-gloss or satin finishes are recommended for trim because they are more durable and easier to clean than flat finishes used on walls.
How should I store leftover paint?
Proper paint storage extends the usable life of your leftover paint significantly. First, ensure the lid is completely sealed by placing plastic wrap over the opening before pressing the lid down firmly. Store paint cans upside down to create an airtight seal. Keep paint in a climate-controlled environment between 50 and 80 degrees Fahrenheit, as extreme temperatures can ruin paint. Avoid storing paint in garages, sheds, or attics where temperatures fluctuate. Label cans clearly with the room name, date, and brand information. Properly stored latex paint lasts 2-10 years, while oil-based paint can last up to 15 years. Before reusing stored paint, stir thoroughly and check for lumps, odd smells, or separation that cannot be remixed.
How accurate is this paint calculator?
This calculator provides reliable estimates based on industry-standard coverage rates and typical door and window dimensions. The calculation uses 350 square feet per gallon coverage, 21 square feet per standard door, and 15 square feet per standard window. Results are accurate for most residential painting projects involving smooth to moderately textured walls. For best results, round up your paint purchase to the next full gallon to account for variables like wall porosity, paint waste, and future touch-ups. The calculator may underestimate paint needs for heavily textured walls, unpainted surfaces, or dramatic color changes. When in doubt, buy an extra gallon, as most stores accept returns of unopened paint.
Painting Tips
- Calculate before buying: Use this calculator to determine exactly how much paint you need before visiting the store. Buying the right amount saves money and prevents project delays. Round up to the nearest gallon and consider purchasing an extra quart for touch-ups.
- Invest in quality paint: Premium paints cost 20-40% more but provide better coverage, requiring fewer coats and less total paint. They also resist fading, staining, and wear better than budget options. Over a paint job's 5-7 year lifespan, quality paint often costs less per year than cheap alternatives that need repainting sooner.
- Proper preparation is essential: Spend adequate time preparing surfaces before painting. Clean walls to remove dust, grease, and cobwebs. Fill nail holes and cracks with spackling compound. Sand rough spots smooth. Remove or tape off outlet covers, light switches, and fixtures. Apply painter's tape to trim, ceiling edges, and windows. Good preparation is the difference between amateur and professional-looking results.
- Consider temperature and humidity: Paint adheres best and dries properly between 50 and 85 degrees Fahrenheit with humidity below 70%. Avoid painting on very humid days, as moisture prevents proper drying and can cause adhesion problems. In winter, ensure adequate heating and ventilation. In summer, avoid painting in direct sunlight, which causes paint to dry too quickly and creates brush marks.
- Maintain a wet edge: Work systematically in sections and always maintain a wet edge where fresh paint meets previously applied paint. Letting edges dry before blending creates visible lap marks in the finished surface.
Paint coverage guidelines
- 1 gallon: Covers approximately 350-400 sq ft
- Standard door: ~21 sq ft (3' x 7')
- Standard window: ~15 sq ft (3' x 5')
Tip: Dark colors or textured walls may require more paint. Always buy a little extra for touch-ups.
When to use multiple coats
- 1 coat: Touch-ups, same color refresh
- 2 coats: Standard for most color changes (recommended)
- 3 coats: Dramatic color changes (light to dark or dark to light)
Did you know?
- The earliest paints, dating back 40,000 years, were made from minerals, charcoal, and animal fat used for cave paintings.
- White and lighter colors reflect more light, making rooms feel larger and potentially reducing cooling costs in warm climates.
- Lead was added to paint for durability until banned in 1978. Always test old paint before sanding or scraping in homes built before this date.
- The color blue was once so expensive to produce that it was reserved for royalty and religious paintings.
- Paint typically accounts for only about 15% of the total cost of a professional painting job, with labor making up the majority.