Katie Hamilton

Article / Updated 10-11-2022

Before you begin painting your home's interior walls, ceilings, woodwork, doors, or windows, you need to estimate the amount of paint you'll use. Estimates require specific calculations for each surface you want to paint. To estimate the amount of paint you need in order to cover the walls of a room, add together the length of all the walls and then multiply the number by the height of the room, from floor to ceiling. The number you get is the room's square footage. Is that math class coming back to you now? How to determine square footage Now you have to determine how much of that square footage is paintable surface area. Because you use a different paint on the doors and windows, subtract those areas from the room total. No sweat, just subtract 20 square feet for each door and 15 square feet for each average-sized window in the room. You end up with a number that is close to the actual wall area you have to cover with paint. In general, you can expect 1 gallon of paint to cover about 350 square feet. You need slightly more than a gallon if the walls are unpainted drywall, which absorbs more of the paint. You also need to consider whether to paint more than one coat. If you're painting walls that are unfinished, heavily patched, or dark in color, plan on applying two coats of paint. When painting a dark color, pros often add a color tint to the white primer. Tints for both latex or alkyd paints are available at most paint stores. For best results, choose a tint shade that's closest to the top coat color. Now for the clincher of the math problem. Divide the paintable wall area by 350 (the square-foot coverage in each gallon can) to find the number of gallons of paint you need for the walls. You can round uneven numbers; if the remainder is less than .5, order a couple of quarts of wall paint to go with the gallons; if the remainder is more than .5, order an extra gallon. Of course, buying in bulk is usually more economical, so you may discover that 3 quarts of paint cost as much as a gallon. Examples of calculations The following examples walk you through the calculations for determining how much paint you need for a 14-x-20-foot room that's 8 feet tall and has two doors and two windows. Ceiling paint calculator Use the following formula to estimate the amount of ceiling paint you need. Double the result if the ceiling requires two coats. 1. Multiply the length of the ceiling times its width to find its area. 14 × 20 = 280 square feet 2. Divide that number by 350 (the estimated square feet covered per gallon) to figure out how many gallons of paint you need. 280 ÷ 350 = .8 For this example, you want to buy 1 gallon of ceiling paint for a single coat. Wall paint calculator Use the following formula to estimate the amount of wall paint you need. Double the result if the walls require two coats. 1. Add together the length of each wall. 14 + 20 + 14 + 20 = 68 feet 2. Multiply the sum by the wall height, to find the total wall area. 68 × 8 = 544 square feet 3. Subtract 20 square feet for each door (20 × 2 = 40) and 15 square feet for each window (15 × 2 = 30) to find the actual amount of wall area you're painting. 544 – 70 = 474 square feet 4. Divide this figure by the paint coverage (350 square feet per gallon), and the result is the number of gallons to purchase. 474 ÷ 350 = 1.4 For this example, you want to buy 1 gallon and 2 quarts of paint for a single coat. Woodwork paint calculator Measure the length of the trim in feet, and multiply that number by 1/2 foot (.5), as a rough size for the width of the trim. Include all the trim around doors and windows, at baseboards, along the ceiling, and for any built-in furniture. As an example, imagine that you have ceiling molding running around a room that is 14 feet wide and 20 feet long. 1. Determine the total length of molding around the room by adding together the length of all the walls that the molding covers. Round the numbers off to the nearest foot. 14 + 20 + 14 + 20 = 68 feet 2. Multiply the sum by .5 for an estimated width of the molding. 68 × .5 = 34 square feet 3. Divide this number by 350 to estimate the gallons of paint required to cover the molding. 34 ÷ 350 = .09 The result in this example is much less than a quart, but you may paint other woodwork in the room the same color, so buying a full quart may not be terribly wasteful. Door and window calculator Use the same figure for estimating door coverage as you use in your wall-area calculations — 20 square feet = one door. Multiply the number of doors by 20, doubling the answer if you plan to paint both sides. Wall paint estimates allow for 15 square feet for each window. Use about half that window area to figure trim and inside sash — the glass isn't important to the calculation. For the room in this example: 1. Multiply the number of doors by 20. 2 × 20 = 40 square feet 2. Multiply the number of windows by 7.5. 2 × 7.5 = 15 square feet 3. Add these numbers together. 40 + 15 = 55 4. Divide the result by 350 (the estimated square feet covered per gallon). 54 ÷ 350 = .16 Often, you end up needing to buy only a quart of paint, which goes a long way on doors and window trim. See also: How to Paint Ceilings and Walls How to Paint Paneled Doors How to Paint Trim Tools You Need for a Basic Paint Project

Article / Updated 04-20-2022

Buying ceramic tile for floors requires measuring and math. Estimate how many ceramic tiles to buy by calculating the total floor area you plan to cover and dividing that number by the size of one tile. Ceramic floor tiles typically come in 4-, 6-, 9-, 12-, and 18-inch squares. First, determine the square footage of the room (don’t forget the closets!); just multiply the room’s length by its width. [Length of Floor] x [Width of Floor] = Total Area. Choose your tile size from the following list and use the accompanying equation to figure out the number of tiles to buy: 4-inch tiles: Total Area ÷ 0.1089 = Number of 4-inch tiles needed 6-inch tiles: Total Area ÷ 0.25 = Number of 6-inch tiles needed 9-inch tiles: Total Area ÷ 0.5625 = Number of 9-inch tiles needed 12-inch tiles: Total Area = Number of 12-inch tiles needed (you’ve measured your room in square feet, and a 12-inch tile is 1 square foot) 18-inch tiles: Total Area ÷ 2.25 = Number of 18-inch tiles needed Because there are variations in the color of tiles from one tile run to another, buy enough tiles to complete the job and have some leftovers for later repairs. You can always bring your room dimensions to a tile dealer, who can help you figure out how much tile and other supplies to purchase.

Cheat Sheet / Updated 03-27-2016

A home improvement project that involves new flooring means using simple math to find the right amount of vinyl or carpet needed for the area you want to cover. If you are planning to paint or wallpaper, use easy formulas to determine how much paint or paper to purchase.

Step by Step / Updated 03-27-2016

When laying floor tiles, getting the room ready is the hardest part. Preparing the room for floor tiles is grunt work, but you’ll soon get to the fun part: laying tiles. You need a pry bar, hammer, nail set, floor cleaner, and lots of pizza for bribing friends and family to help.

Step by Step / Updated 03-27-2016

Before refinishing a hardwood floor, you need to know how to get the floors ready for sanding. The way you get floors ready for sanding affects the final finish, so prepare carefully. The sanding process also creates fine sawdust that can permeate the house if you’re not painstaking in your preparations.

Step by Step / Updated 03-27-2016

Knowing how to stain and seal a hardwood floor properly pays off in having a beautiful finish and enduring protection. Staining and sealing hardwood floors the right way — whether you’re refinishing, refurbishing, or stripping the wood floor — results in years of enjoyment.

Article / Updated 03-26-2016

Does your home improvement project involve a new vinyl floor? To figure out how many vinyl floor tiles, or sheet vinyl, you need, follow these simple formulas: Vinyl floor tile calculator To figure out how many vinyl floor tiles you need to buy, calculate the floor area you want to cover and divide that number by the size of one tile: Floor Area: [Length of Floor] × [Width of Floor] = Floor Area Tiles to Order: For 9" Tiles: Floor Area ÷ 0.5625 = Number of 9" Tiles Needed For 12" Tiles: Floor Area = Number of 12" Tiles Needed Sheet vinyl flooring calculator Determine how much sheet vinyl to purchase by calculating the square footage of floor you plan to cover and dividing that number by 9 to get the number of square yards of flooring you need. Floor Area: [Length of Floor (ft.)] × [Width of Floor (ft.)] = Floor Area (sq. ft.) Sheet Vinyl to Order: [Floor Area] ÷ 9 = Number of Sq. Yards of Floor Covering Needed

Article / Updated 03-26-2016

If you’ve decided on wallpaper for your home improvement project, you want to make sure to buy the right amount for your needs. These formulas help you determine how much wall paper to purchase: Wall Area: [Total Length of All Walls] x [Wall Height] = Wall Area Unpapered Areas: [Window Height] x [Window Width] x [Number of Windows] = Window Area [Door Height] x [Door Width] x [Number of Doors] = Door Area Wallpapering Area: [Wall Area] – [Unpapered Areas] = Wallpapering Area Wallpaper to Order: [Wallpapering Area] ÷ [Usable Yield] = Number of Single Rolls Needed Usable Yield Charts: Pattern Repeat (Drop) Usable Yield (American Rolls) Usable Yield (European Rolls) 0 to 6 in. 32 sq. ft. 25 sq. ft. 7 to 12 in. 30 sq. ft. 22 sq. ft. 13 to 18 in. 27 sq. ft. 20 sq. ft. 19 to 23 in. 25 sq. ft. 18 sq. ft.

Article / Updated 03-26-2016

To avoid having too much leftover wall paint, use these formulas to determine how much paint to buy when you start your home improvement painting project. Total Wall Area: [Total Length of All Walls] × [Wall Height] = Total Wall Area Unpainted Areas: [Window Height] × [Window Width] × [Number of Windows] = Window Area [Door Height] × [Door Width] × [Number of Doors] = Door Area Paintable Wall Area: [Total Wall Area] – [Window Area] – [Door Area] = Paintable Area Paint to Order: [Paintable Area] ÷ 350 = Number of Gallons Needed for Smooth Walls [Paintable Area] ÷ 300 = Number of Gallons Needed for Rough, Textured Walls or Unpainted Wallboard

Article / Updated 03-26-2016

If your home improvement plan involves a new ceramic tile floor, how do you determine the amount of ceramic tiles you need? Simply calculate the area you plan to cover and divide that number by the size of one ceramic tile. Total Area (Floor, Wall, Countertop): Length (ft.) × Width (ft.) = Total Area (sq. ft.) Tile to Order: For 4" Tiles: Total Area ÷ 0.1089 = Number of 4" Tiles Needed For 6" Tiles: Total Area ÷ 0.25 = Number of 6" Tiles Needed For 9" Tiles: Total Area ÷ 0.5625 = Number of 9" Tiles Needed For 12" Tiles: Total Area = Number of 12" Tiles Needed For 18" Tiles: Total Area ÷ 2.25 = Number of 18" Tiles Needed