Estimate wall area, paint volume, can count, and total paint cost—with doors, windows, coats, and waste included.
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DECISION GUIDE
How to use this result in a real decision.
How much paint should be purchased without treating every wall as a perfect, single-coat surface? Start with net wall area, multiply by the planned coats and waste allowance, then divide by the coverage printed on the actual product label. Round up only after calculating the total volume.
WORKED EXAMPLE
A 12 ft × 12 ft room with 8 ft walls
Inputs
384 sq ft of gross wall area, 50 sq ft of doors and windows, two coats, 350 sq ft per gallon and 10% waste.
Calculated result
Net area is 334 sq ft. Two coats plus waste require about 2.10 gallons, so three 1-gallon cans are needed if that is the available size.
Decision meaning
The third can is not evidence that 3 gallons will be used. It is the purchase quantity after openings, coats, coverage and package size are made explicit.
Check before acting
Use the coverage range on the selected paint rather than a generic average.
Measure each opening and decide separately whether the ceiling, doors and trim are included.
Increase the allowance for porous repairs, heavy texture or a major color change.
Not included automatically
Primer, ceiling paint and separate trim or door coatings
Labor, tools, masking materials and surface repair
Product-specific drying, recoat and application requirements
How to use it
A better estimate in three steps.
01
Enter the room dimensions and subtract openings.
02
Set coats and the coverage printed on your paint can.