How to Calculate How Much Paint You Need

paint roller and brush

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If you're embarking on a paint project, the last thing you want is to spend too much or too little on the paint you need. Buy too little and you're interrupting your project to run back to the store, and buy too much and you're stuck with cans that you can't safely dispose of. Before rolling up the sleeves, make sure you know how to calculate how much paint you'll need. An easy-to-use paint calculator will help you figure out how much paint is necessary for your home improvement activity while staying within a comfortable range. Also, we helped you out by calculating paint quantities for a few basic room types. These are rough estimates; precise paint needs will vary according to your project.

General Calculation Tips

As a rule of thumb, always plan to have enough for two coats of paint. Take the square footage of your ceiling into your personal calculation if you'd like to include it in your paint project. As applicable, you should make sure that windows, entry doors, and non-paintable areas such bathtubs, surrounds, cabinets, and tiled areas are not included (because who wants to paint their tub?). Painting projects for entire rooms are based on a wall coverage factor of 350 square feet per gallon of paint. If you're unsure of exactly how much paint you need, we included some average estimates below.

How to Calculate Square Footage for Painting

The square footage, or area, of a wall is determined by multiplying the width of the wall by the height of the wall. The area of each wall should be calculated individually. After all wall areas are determined, these figures are added together. Since doors and windows do not receive paint, you should exclude them by subtracting their combined areas. Ceiling square footage is calculated by multiplying the width of one wall by the width of an adjacent wall. No exclusions are made for ceiling elements such as light fixtures or smoke alarms.

Bathroom Painting

How Much Paint to Use for a Powder Room

  • Floor Size: 20 square feet
  • Wall Space: 124 square feet
  • Use: 1 gallon of paint

Because they have no bathtub or shower, powder rooms walls are usually in such good condition that two coats with one gallon of paint is sufficient. This sample calculation excludes 20 square feet for one entry door from the total wall space. Powder rooms tend not to have windows.

How Much Paint to Use for a Small Bathroom

  • Floor Size: 40 square feet
  • Wall Space: 108 square feet
  • Use: 1 gallon of paint

For a small bathroom with minimal wall problems, you can usually purchase just one gallon of paint. This calculation excludes one entry door, one window, and 65 square feet of wall space for a bathtub and surround.

How Much Paint to Use for a Medium Bathroom

  • Floor Size: 120 square feet
  • Wall Space: 252 square feet
  • Use: 2 gallons of paint

For this bathroom calculation, excluded are both a window and an entry door, along with 65 square feet for the tub/surround.

How Much Paint to Use for a Large Bathroom

  • Floor Size: 160 square feet
  • Wall Space: 316 square feet
  • Use: 2 gallons of paint

For this large bathroom, two gallons of paint will comfortably cover all wall areas with a little paint to spare. This calculation excludes both a window and an entry door from the total wall space. An alcove tub and surround calculated at 65 square feet of wall space are excluded, as well.

Kitchen Painting

Kitchens are heavy-use areas, so they always require a thorough paint job. At the same time, kitchens tend to have limited wall space due to the base and wall cabinets, reducing the amount of paint you will need. Buy quality paint in eggshell or semi-gloss sheens for easier kitchen cleanup.

How Much Paint to Use for a Small Kitchen

  • Floor Size: 100 square feet
  • Wall Space: 243 square feet
  • Use: 2 gallons of paint

Plan on purchasing two gallons of paint for all types of small kitchens. One door, one window, and 42 square feet of base and wall cabinets are excluded from the wall space square footage.

How Much Paint to Use for a Medium Kitchen

  • Floor Size: 200 square feet
  • Wall Space: 383 square feet
  • Use: 2 gallons of paint

Use two gallons of paint for two coats of paint in average-sized kitchens. One door, one window, and 62 square feet of base and wall cabinet space are excluded to produce the total wall space.

How Much Paint to Use for a Large Kitchen

  • Floor Size: 300 square feet
  • Wall Space: 515 square feet
  • Use: 3 gallons of paint

The sample net calculation of paint for a large kitchen excludes two windows and one door from the total wall space, along with 75 square feet of base and wall cabinet space.

Bedroom Painting

Bedrooms use a lot of paint. Though walls are usually in good condition and rarely require more than two coats of paint, there usually is a lot of wall space since most bedrooms have few built-in obstructions.

How Much Paint to Use for a Small Bedroom

  • Floor Size: 150 square feet
  • Wall Space: 345 square feet
  • Use: 2 gallons of paint

The sample net calculation excludes both a window and two doors from the total wall space. One door is the entry door. The other door is a single-width closet door occupying 20 square feet of unpainted wall space.

How Much Paint to Use for a Medium Bedroom

  • Floor Size: 200 square feet
  • Wall Space: 405 square feet
  • Use: 3 gallons of paint

Medium-sized bedrooms will use about three gallons of paint. With this calculation, one window and three doors are excluded. One of those doors is an entry door. The other two doors account for a double-width closet door that uses 40 square feet of unpainted wall space.

How Much Paint to Use for a Large Bedroom

  • Floor Size: 300 square feet
  • Wall Space: 565 square feet
  • Use: 4 gallons of paint

With this large master bedroom calculation, excluded are one entry door, one window, and two additional doors to account for a double-width closet occupying 40 square feet of unpainted wall space.