Paint Calculator

Useful for interior or exterior projects this paint calculator can help you estimate how much paint you need for your paint job. Whether you are painting one room, many rooms, or the exterior of a house, just measure the height and width of the surfaces you need to paint.

Calculate Amount of Paint

Enter the dimensions in the calculator to estimate how many gallons of paint you need. You can enter dimensions of a room, a wall, trim or molding. If you need to paint many rooms, or a home exterior, enter the pre-calculated total area of square footage for your project.

While you want to be sure your estimate includes all surfaces you'll be painting, the calculator can subtract openings like windows and doors that won't be painted, or require a different paint. Enter the quantity and dimensions of doors and windows to subtract these openings from the total room, wall or building area.

For trim paint, enter the baseboard, crown molding or door and window trim dimensions to get an accurate paint estimate. If your molding has a lot of curves or a complex profile be sure to add a little extra to your paint estimate.

How Much Paint Coverage per Gallon

Interior and exterior paint are formulated differently to account for varying durability, safety and finishing textures or sheens. You should not substitute interior paint for exterior paint, or vice versa.

Likewise, different interior and exterior surfaces affect how much area is covered by a gallon of paint. Generally, exterior spaces like fences, houses and decks require less paint. Although if the surface is very porous you may need more paint than expected.

You may be wondering how many square feet a gallon of paint covers. Estimated coverages per gallon for different surface textures are provided below. Keep in mind that these are general guidelines and that your particular surface application may vary.

Expected Paint Coverages

• Smooth drywall interior: 400 ft² per gallon
• Textured interior: 350 ft² per gallon
• Wood siding: 275 ft² per gallon
• Stucco: 175 ft² per gallon
• Brick: 200 ft² per gallon

Check the label of your particular brand, sheen, and type of paint to find the expected coverage number per gallon. You'll need this for the calculator when you specify the number of coats and coverage per gallon. Enter price per gallon or liter for an optional cost estimate.

If you have irregular shapes, split the space into smaller zones and calculate those areas before adding them together for the total. Then use the Known Area option in the project drop down menu.

The paint calculator supports both US and metric units, offering the answer in gallons, quarts and liters.