Paint Calculator
Estimate paint and primer for walls and ceilings. Accounts for doors, windows, multiple coats, and waste factor.
Paint Settings
Typically 350-400 sq ft/gal
Typically 400 sq ft/gal
Touch-ups, spills, overage
Paint Estimate
gallons needed
gallons needed
Paint: $105
Primer: $50
Painting Tips
- Always prime bare drywall or dark color changes
- Buy all paint at once for color consistency
- Add 10% extra for touch-ups later
- Coverage varies by surface texture
How Much Paint Do I Need?
Whether you are planning to repaint your bedroom or are going to paint all the rooms in your brand-new house, this interior paint calculator is here to help you determine how much paint you need. You will be able to find the paint estimation based on the number of openings or the number of coats of paint. You can also calculate the final cost of paint required!
What You Need to Input
You will have to input some raw data into the paint calculator. It includes:
- 1Room dimensions — You need to type in the length, width, and height of the room you plan to paint. If your room has a different shape than a rectangular cuboid, you can also input the total room wall area directly into the paint estimator. The calculated value only takes into account the walls as if there are no doors or windows.
- 2Doors — You can use the default dimensions of a door entered in our calculator or customize them to fit your needs. Make sure to type in the number of doors in the room so the paint calculator will find their total area. Enter 0 if the room to be painted has no doors on the wall.
- 3Windows — Again, you can utilize the default dimensions provided or type in custom ones. Then, enter the number of windows of the same dimensions. Don't forget to input the number of windows, whether 0 or more. If you have windows of different sizes in your room, it's better to calculate the total area manually and input this value into the appropriate box.
- 4Number of coats — By default, our calculator finds the amount of paint required for one layer, but you can input the number of coats you plan to use yourself. Most projects require 2 coats for best results.
- 5Paint efficiency — This number should be written on the paint can, expressed in m²/l or ft²/l. Most standard paints cover 350-400 square feet per gallon.
- 6Cost per unit volume — Optionally, you can input the cost of a unit of paint (cost per liter or per gallon). The paint calculator will automatically find the total cost of paint.
Is the Paint Estimation Accurate?
Obviously, it won't be a hundred percent accurate. Several factors can affect the actual amount of paint needed:
- •If the surface is porous or rough, it will require additional paint — up to 20%.
- •Similarly, complicated fittings require extra paint.
- •You also need to add some paint — up to 30% — if you are painting a surface for the very first time, as you need to prepare the wall with primer.
- •Dark color changes (like painting over deep red with white) may require additional coats and primer.
Our interior paint calculator includes a waste factor adjustment to help account for these variables.
What About the Ceiling?
Our calculator includes an option to paint the ceiling! Simply check the "Paint ceiling" box in any room, and we'll automatically calculate the ceiling area (length × width) and add it to your total. Ceiling paint typically requires less paint per square foot than walls due to smoother surfaces.
Tips for Accurate Paint Estimation
Buy All Paint at Once
For color consistency, purchase all your paint in one batch. If you need to buy more later, the color may vary slightly between batches.
Round Up, Not Down
Always round up to the next whole gallon. It's better to have a little extra for touch-ups than to run short mid-project.
Don't Forget Primer
New drywall, bare wood, or drastic color changes need primer. Use our primer calculator to estimate primer needs separately.
Check the Paint Can
Coverage rates vary by brand and paint type. High-quality paints often cover more area per gallon than budget options.
How It Works
Calculate Area
Wall area = perimeter × height. Ceiling = length × width. Subtract doors and windows.
Apply Coats & Waste
Multiply by number of coats. Add waste factor (typically 10%) for touch-ups and spills.
Estimate Gallons
Divide total area by coverage rate (350-400 sq ft/gallon). Round up to whole gallons.
Need to measure your wall area first? Calculate your room's square footage before estimating paint.
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