Free Paint Calculator

To calculate how much paint you need, determine the net painting surface area by multiplying each wall's Length × Height and subtracting the areas of doors and windows. A standard room with 400 square feet of wall space requires approximately 1.15 gallons of paint per coat. For a standard 2-coat job, you will need approximately 2.3 gallons of paint, meaning you should purchase 3 gallons to cover the work and have leftovers for touch-ups.

For brand new drywall or fresh plaster walls, the standard professional application process consists of five total coats: 2 coats of wall putty (to smooth out the surface and fill pores), followed by 1 coat of primer (to seal the surface and ensure even adhesion), and finished with 2 coats of premium emulsion wall paint to achieve the desired color depth and hide.

Under standard field conditions, one US gallon of high-quality interior latex paint covers between 350 and 400 square feet of smooth, primed drywall with a single coat. If you are painting raw, unprimed drywall, textured stucco, or porous masonry walls, the coverage rate decreases significantly to around 200 to 250 square feet per gallon because the surface absorbs more paint.

A single gallon of wall primer typically covers between 300 and 350 square feet. You only need a single coat of primer for most residential projects, meaning you should divide your net wall area by 300 to find the required gallons. Primer is highly recommended when painting over new drywall, raw plaster, patched sections, or when making a drastic color change (e.g., from dark blue to white).

For a standard double-coat application, wall putty has a coverage rate of approximately 10 to 15 square feet per kilogram, which translates to about 0.07 to 0.10 kilograms per square foot. Wall putty is used to level out minor plaster depressions and surface rough spots. For a 100-square-foot wall, you will need approximately 8 to 10 kg of dry putty powder.

Latex-based paint (water-based) is the residential standard for interior walls and ceilings. It dries quickly, has low odor, and cleans up easily with soap and water. Oil-based paint (alkyd) is highly durable and smooth, making it ideal for high-traffic surfaces like baseboards, moldings, doors, and cabinets. However, oil-based paint takes longer to dry and requires mineral spirits or paint thinner for clean-up.

To find the gross wall area of a room, measure the perimeter (sum of all wall lengths) and multiply it by the ceiling height. For example, a 12x15 foot room with 8-foot ceilings has a perimeter of 54 feet (12+12+15+15). The gross wall area is 54 × 8 = 432 square feet. You must deduct the areas of doors and windows from this total before calculating your paint order.

Since you do not paint over glass windows and wooden doors with wall paint, you must deduct their surface areas from your gross wall area. A standard interior door is 3 ft × 7 ft (21 sq ft) and a standard double-hung window averages 3 ft × 5 ft (15 sq ft). Subtracting these voids prevents you from over-purchasing paint, particularly in rooms with multiple openings.

A standard waste factor of 10% is recommended for residential interior painting. This allowance accounts for paint absorbed by the roller cover nap, paint left at the bottom of the can, spills, and future touch-ups. For complex layouts with numerous built-ins, shelves, or columns, increase the waste factor to 15% to cover brush-cutting losses.

A standard 5-gallon commercial paint bucket contains exactly 5 US gallons of paint. Purchasing paint in 5-gallon buckets is highly recommended for large projects (like painting entire houses or large ceilings) because bulk buckets are 15% to 25% cheaper per gallon than buying five individual 1-gallon cans.

A 12x12 foot room with standard 8-foot ceilings has a gross wall area of 384 square feet. Deducting a standard door and window leaves a net area of approximately 348 square feet. A 2-coat painting job requires 696 square feet of coverage. Dividing by the standard coverage rate of 375 sq ft/gallon, you will need exactly 1.85 gallons. You should purchase 2 gallons of wall paint.

Yes, heavy wall textures (such as knockdown, orange peel, popcorn, or exterior stucco) increase the physical surface area compared to flat drywall. Textured surfaces require about 20% to 30% more paint to achieve complete coverage, as the roller must apply paint into all the micro-crevices. Adjust your calculator inputs by adding to the waste factor when estimating for textured walls.

For standard water-based latex paints, you should wait at least 2 to 4 hours before applying a second coat. While latex paint may feel dry to the touch within 1 hour, applying a second coat too early can pull up the first layer, causing clumping, streaks, and poor adhesion. For oil-based paints, wait a minimum of 24 hours between coats.

These terms describe the paint sheen (reflection level). Matte (flat) has no sheen, hiding wall defects well but staining easily. Eggshell and satin have a soft luster, offering the ideal balance of hide and washability for living rooms and bedrooms. Semi-gloss and high-gloss are highly reflective, moisture-resistant, and easy to clean, making them perfect for kitchens, bathrooms, trim, and doors.

To calculate ceiling paint, multiply the room's Length × Width to find the square footage. Ceilings are rarely textured like walls, so a standard coverage of 350 to 400 square feet per gallon applies. For a 15x20 foot room, the ceiling area is 300 square feet, meaning you will need approximately 0.85 gallons per coat. A single coat of flat white ceiling paint is standard.

No, you should never paint directly over raw drywall without applying a primer coat first. Raw drywall paper and joint compound are highly porous and absorb moisture unevenly. Painting directly will result in a blotchy finish, visible seams (shadowing), and peeling. A dedicated PVA primer seals the drywall, ensuring a uniform topcoat finish.

To calculate exterior siding paint, find the total surface area of all exterior walls (excluding doors and windows) and add a 10% to 15% waste factor. Exterior paint must withstand weather elements, so 2 coats are mandatory. If you are painting rough wood siding or textured stucco, expect coverage to decrease by 25%, and adjust your paint volume order accordingly.

One liter of standard emulsion wall paint covers approximately 10 to 12 square meters (approx. 100 to 130 square feet) per coat on a smooth, primed surface. For a standard two-coat job, one liter of paint will finish about 5 to 6 square meters of wall space. Divide your total area in square meters by 10 to estimate your liter requirements.

You should apply a minimum of two coats of wall putty to new plaster walls. The first coat fills deep plaster pores and levels major uneven patches. The second coat is a thin skim coat that provides a glass-smooth surface. After the second coat dries, sand the wall with fine-grit sandpaper (220-grit) and wipe away dust before priming.

Paint peels primarily due to poor surface preparation, moisture trapped behind the paint film, or painting over dirty, greasy, or glossy surfaces. Prevent peeling by cleaning walls thoroughly, repairing plumbing leaks, installing bathroom exhaust fans to control humidity, sanding glossy surfaces, and always applying a dedicated primer before painting.

For interior and exterior painting, the ideal temperature range is between 50°F and 85°F. If the temperature is below 50°F, water-based latex paint cannot form a proper film, resulting in cracking and peeling. In extreme heat (above 90°F), the paint dries too quickly, causing brush lap marks, skinning, and poor surface leveling.

Even if the color formula is identical, slight mixing variations occur between paint cans. To ensure uniform color, painters use a technique called 'boxing'. Pour all the paint cans of the same color into a clean 5-gallon bucket and stir them together thoroughly before starting. This blends any color differences, ensuring a consistent finish across walls.

To calculate trim and baseboard paint, measure the total linear feet of all trim boards. A standard baseboard is about 4 inches wide. Multiply the linear feet by 0.33 feet to find the square footage. For example, 150 linear feet of trim equals 50 square feet. A single quart of semi-gloss trim paint covers about 100 square feet, which is enough for 2 coats.

For water-based latex paint, scrape excess paint back into the can, then rinse the rollers and brushes under warm running water, using a drop of dish soap to break down binders. Use a paint comb to clean brush bristles. For oil-based paint, soak the brush in a container of mineral spirits or paint thinner, squeeze out excess liquid, and dry flat.

Do not throw wet paint in the household trash or pour it down the drain, as it can contaminate water systems. If you have a small amount of latex paint left, leave the lid off in a well-ventilated area until it dries solid. For larger amounts, mix in a commercial paint hardener or kitty litter to solidify the paint before throwing the can in the trash.