Flooring & Finishes
Flooring Calculator
Calculate square footage, boxes of flooring and total cost with the right waste for your layout.
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Flooring & Finishes
Paint Calculator
Estimate how much paint you need for a room. The calculator subtracts doors and windows, applies your number of coats and suggests how many gallons and quarts to buy.
What is a paint calculator?
This calculator estimates wall paint for a rectangular room. It is designed for the practical question at the store: how many gallons and quarts should I buy?
How does it work?
Perimeter × wall height gives the gross wall area. Standard allowances are removed for doors (20 sq ft) and windows (15 sq ft). The remaining area × coats ÷ coverage gives gallons, split into whole gallons and quarts. Adding panelling below a chair rail? The Wainscoting Calculator covers the lower wall, and the Flooring Calculator finishes the room.
What information is needed?
- Room length, width and wall height in feet
- Number of doors and windows
- Number of coats
- Coverage per gallon from the can
How to use the Paint Calculator
- Measure the room and wall height.
- Count doors and windows.
- Choose coats and check coverage on the label.
- Select Calculate.
The formula
In plain terms, here is the calculation the tool runs:
Wall area = 2 × (L + W) × H
Paintable = Wall area − 20·Doors − 15·Windows
Gallons = Paintable × Coats ÷ Coverage
- L, W, H
- Length, width, height in feet
- Coverage
- Sq ft per gallon, usually 350–400
Worked example
Example
A 14 × 12 ft bedroom with 8 ft walls, one door, two windows, two coats at 350 sq ft/gal.
- 2 × (14 + 12) × 8 = 416 sq ft
- 416 − 20 − 30 = 366 sq ft
- 366 × 2 ÷ 350 = 2.09 gallons
Buy 2 gallons and 1 quart.
Frequently asked questions
Does this include the ceiling?
No. Ceiling area is length × width — 168 sq ft for a 14 × 12 room. Ceiling paint is usually bought separately.
Do I need primer?
Prime new drywall, repairs and stained areas. Primer coverage is similar, so run the calculator again with one coat.
How much for trim?
A quart covers the trim, doors and window casings in a typical bedroom.
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