How much primer do i need calculator

Painting a room can be a quick and inexpensive way to refresh your space. But can often leave even experienced DIY’ers wondering, “How much paint do I need?” Knowing the right paint coverage to get the job done can ensure any DIY project is completed on time, on budget, and with as minimal hassle as necessary. No one wants to make last-minute runs to a home improvement store because a paint can is suddenly empty and you don’t have enough for a second coat. Nothing is more frustrating when the brushes are wet and you realize there’s not enough paint to finish your living room.

On the flip side, an excess of custom paint color your ordered to polish off your kitchen cabinets will sit in your garage. A typical paint shelf life is around two years (but that can vary by brand and formulation). “Buying too much or too little paint can lead to complications,” says Mike Mundwiller, end user product experience manager at Benjamin Moore. “Buying too much is not environmentally friendly, and buying too little could cause color differences.” Boxing, or combining two or more gallons of paint, ensures that you will have consistent color development. “When working with more than one gallon of paint, it is best to ‘box’ your material,” he adds. “If you do not ‘box’ your paint, two walls could look slightly different.”

Here, paint experts offer even more advice on figuring out how the number of gallons (or perhaps just quarts of paint) are needed for painting walls, no matter the surface area or the height of the walls. 

How do I calculate how much paint I need?

To determine how much paint you’ll need for your painting project, you’ll want to grab a tape measure and maybe a calculator—depending on your math skills. If you’re painting a room (of anything for that matter), you need to determine how many square feet you intend to cover. When measuring a wall, don’t include baseboards, crown molding, or other trim, as you’re likely to be painting those with a different type of paint or color.

Here’s how to get an accurate estimate:

  • Measure the length of each wall of the room (in feet, round up if you have to), and add them together
  • Measure the height of the walls (in feet, round up if you have to)
  • Multiply those two numbers together to get the square footage of the area
  • Subtract 20 square feet per door in the room (or recalculate if you have a custom door)
  • Subtract 15 square feet per window in the room (or recalculate if you have a custom window)
  • Once you have your total, divide by 400 to determine how many gallons of paint you need for one coat of paint.

Let’s practice and figure how how much paint is needed for a 12x12 room:

  • 12 + 12 + 12 + 12 = 48 feet of wall area
  • Our walls are 12-feet high
  • 48 x 12 = 576 square feet of area
  • Three doors (one room door and two closet doors) x 20 = 60 square feet [576 - 60 = 516]
  • Two windows x 15 = 30 square feet [516 - 30 = 486]
  • 486 / 400 = 1.2 gallons of paint needed per coat

Whether you’re painting a powder room or the exterior of your house, paint coverage is fairly universal. The general rule of thumb is one gallon per 400 square feet. But that’s just a rough guideline: To get a more precise number, which you’ll definitely want for large projects, you can also use a paint calculator or paint estimator like the ones provided by Benjamin Moore, Backdrop, Pratt & Lambert or Sherwin-Williams; they take into account window and door measurements.

How do I calculate how much paint I need for one wall?

If you’re planning a dramatic accent wall, you won’t need to determine the surface area of the entire room. Instead, you’ll just multiple the width by the height of the wall you’re painting. So if it’s a 10-foot wall with a standard 8-foot ceiling, you’ll need enough paint to cover 80 square feet. Likewise, this formula will also tell you know much paint you need for a ceiling.

How do I calculate how much paint I need for smaller projects?

Planning to paint cabinets or furniture? Use the same equations as above, multiplying height times width to get the paintable surface area, tacking on a bit extra for things like table legs. Typically a quart of paint should cover a DIY furniture project or if you want to repaint a fireplace surround. For something very small, like painting the frame of a mirror or stenciling a design, a sample-size container is enough paint.

What area does one gallon of paint cover?

A gallon of paint typically covers around 400 square feet with a single coat, says Natalie Ebel, co-founder of Backdrop, a paint company, who recommends a second coat for optimal coverage that shows off the paint color’s depth and nuance. “In terms of scale, a regular-size bathroom could be one to two gallons, while a regular-size bedroom is often two to three gallons,” she says. Remember, coverage will vary a bit based on the texture of your walls, how thickly you’re applying the paint and the color you’re using or attempting to cover up. For instance, if you know that you will be covering a dark wall with a light paint color, you will most certainly want to have a second coat, even after priming. The coverage also depends on the quality of paint. Keep in mind that better paint is congruent to the raw materials used, like acrylic resins and rich pigments, adds Ebel. It depends on the brand, but typically high quality paint may only need one coat.   

What area does one quart of paint cover?

Don’t forget, paint comes in smaller amounts than gallons, and sometimes a quart is all you need. One quart will typically cover 100 square feet of surface area. “When working with a quart of paint, I recommend focusing on a small room or transitional space, such as a mudroom, powder room, or entryway to make sure you have enough paint for the entire project,” says Sue Wadden, director of color marketing at Sherwin-Williams. “These small spaces provide the perfect opportunity to make a statement with a tone that you may not be ready to invest in a larger quantity of yet. Don’t be afraid to make a bold choice in a small space—I love using a cozy room to play with colors and patterns.” Wadden recommends a dramatic jewel tone, like an aubergine (Carnelian SW7580) or a deep teal (Blue Peacock SW0064), which can really envelop you in the space for a small powder room. For a mudroom or a transitional space like an entryway, she likes a rich neutral, like the smoky Urbane Bronze SW7048 or pinkish Redend Point SW9081. If you happen to have paint left over, create a monochromatic look by painting the ceiling or trim in the same color.

Does this calculation work for all paint brands?

Most paint cans will cover around a 400-square-foot surface area. “If the main calculating factor is coverage, based on volume solids and dry film thickness, then it is the same,” Mundwiller says. “It is important to not confuse volume solids as an indicator of paint quality. The thickness [viscosity] of paint is also not an indicator of quality.” Premium brands and lines typically boast a higher-coverage area because the paint formula is more balanced and contains more pigments, whereas more budget-friendly options may not guarantee as much coverage, or hide, and may require a number of coats. While the difference shouldn’t be as vast as you needing an extra gallon of paint, you may need an extra quart of paint when painting a large space such as a living room. Always check the label of the brand you intend to buy to get the exact coverage amount before finalizing your calculations.

Will the same calculation work for primer?

Yes, the calculation will work, but it will need a little tweaking. Though the same size as a regular paint can, most primers only cover 200 to 300 square feet, so a gallon of primer won’t go as far as a gallon of paint. The main reason is that you want to make sure you apply a second coat of primer since the goal is to prep the wall area for paint color. Check the label on the primer you intend to use to get its unique coverage area and adjust your calculations accordingly. Remember, priming will help paint go on more smoothly and evenly, so this is an important step.

Will this calculation work when painting over darker colors too?

Planning on whitewashing a charcoal gray wall? You’ll likely need additional paint when going from dark to light. On the other end of the spectrum, a deep color base tends to require more coats of paint than a lighter color, says Carolyn Noble, color marketing and design manager at Pratt & Lambert. She recommends applying a gray-tinted primer to the surface before you paint your walls a saturated paint color to help reduce the number of applications. When it comes to finish, you may have heard the glossier it is, the higher the coverage rate, but it’s not enough to change the number of gallons you need to buy, Mundwiller says.

What else should DIY’ers keep in mind when it comes to paint coverage?

If you’re painting a highly textured surface, like stucco, rather than a smooth one, buy a little extra, says Julianne Simcox, Pratt & Lambert associate brand manager. Kitchen cabinets with complicated millwork require more paint too.

The quality of your paint supplies can also have a big impact. Roller covers, for one, can dictate how paint is absorbed. Backdrop makes a 9-inch and a 4-inch roller cover that prevents shedding and streaks. “How much paint you put on your brush and roller will have a big impact,” Ebel says. “We often see first-time painters applying a first coat that might be too thin. You really want a nice rich coat of paint.” That said, don’t load so much paint on your roller that it globs all over the wall. “The best thing to do is thoroughly coat your roller cover in the paint tray so that it's fully saturated with paint,” Ebel says. “Then roll over the textured part of the tray to remove some excess and dripping paint before moving on to the wall surface.”

Mundwiller suggests purchasing about 10 percent more than calculated. His best advice? Ask questions at the paint shop or hardware store before you haul those paint cans home. “Many consumers, and sometimes even the pros, overlook the obvious step of getting advice,” he says. “Every job has some unique aspects that an experienced associate can help sort out.”

How do you calculate how much primer you need?

Primer only covers 200-300 sq. ft. per gallon, so you'll need slightly more primer than paint. Take your earlier total area and divide that number by 300 to get the minimum gallons of primer you'll need for one coat.

How much will a 5 gallon bucket of primer cover?

Easy to apply by brush, roller or sprayer and covers approximately 180-200 sq. ft.

How many sq ft will a gallon of primer cover?

Paint usually is applied at 350 to 400 square feet per gallon (primer at 200 to 300 square feet per gallon). Use the Area section below to calculate the walls and ceiling values.

How many square feet will 5 gallons of Kilz primer cover?

This is a 5-gallon bucket of KILZ 2 Latex Water-Based Primer, Sealer, and Stainblocker for interior and exterior surfaces in white. Covers approximately 300-400 square feet per gallon. Use on properly prepared surfaces free of dust, grease, chalk, rust and peeling paint. Mix well before using.