How Much Paint Do I Need?
The amount of paint you need depends on the surface area, the number of coats and the coverage rating of the paint. For a room, the wall area can be estimated from the room perimeter multiplied by the wall height. Doors and windows are then subtracted from the paintable surface.
How to Use the Paint Calculator
- Select Walls or Walls + Ceiling.
- Enter the room length, width and wall height.
- Enter the number of doors and windows and their average areas.
- Choose the number of coats you plan to apply.
- Enter the paint's coverage rating from the product label.
- Add an extra percentage for touch-ups and application loss.
- Optionally enter the price per gallon for an estimated paint cost.
Paint Calculator Formula
After subtracting doors and windows, the calculator multiplies the remaining paintable area by the number of coats. It then divides by the paint's coverage per gallon and applies the selected extra allowance.
Walls + Ceiling Formula
The ceiling is included only when the Walls + Ceiling option is selected. If your ceiling has an unusual shape, measure that surface separately for a more accurate estimate.
Why Does Paint Coverage Matter?
Coverage varies by product and surface. A smooth previously painted wall may require less paint than a porous or textured surface. Always use the coverage information supplied by the paint manufacturer when available.
How Many Coats of Paint Do I Need?
Two coats are commonly used for many interior painting projects, but the appropriate number depends on the existing color, paint type, surface condition and desired finish. A primer may also be appropriate for some surfaces or major color changes.
Why Add Extra Paint?
A small allowance can help account for roller or brush loss, touch-ups, uneven absorption, spills and future repairs. Keeping a small amount of the original paint can also make matching future touch-ups easier.
Important Painting Note
This calculator provides a planning estimate rather than a guarantee of coverage. Product labels and manufacturer specifications should take priority, especially for specialty coatings, exterior surfaces, porous materials and major color changes.