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Paint Project Calculator and Shopping List
Paint projects go more smoothly when you know roughly how many gallons to buy before you are standing in the aisle. This calculator estimates wall area, optional ceiling area, coats, primer, and material cost using your room measurements.
Planning note
How this calculation works
- Wall area is estimated from room perimeter multiplied by ceiling height, then reduced by a standard allowance for doors and windows.
- Paint gallons are based on adjusted paintable area multiplied by the number of coats, divided by the coverage per gallon you enter.
- Primer gallons are estimated separately when primer is included, using the same paintable surface area.
Assumptions and limitations
- Door and window sizes vary, so the tool uses common planning allowances rather than exact measurements.
- Textured walls, dark color changes, porous surfaces, and spraying can require more paint.
- Prices exclude brushes, rollers, tape, trays, patching compound, sales tax, and delivery.
Worked example
For a 12 by 14 foot room with 8 foot ceilings, 2 doors, 2 windows, and 2 coats at 350 square feet per gallon, the tool estimates the paintable area and rounds gallons up for shopping.
FAQ
Should I buy extra paint?
Often yes. A small cushion helps with touch-ups, roller loss, color matching, and surfaces that absorb more than expected.
Does this subtract doors and windows?
Yes, it subtracts a simple planning allowance for each door and window. Measure exact openings if you need a tighter estimate.
When should I include primer?
Primer is commonly useful for new drywall, patched areas, stains, bare wood, or major color changes. Follow the paint manufacturer's guidance.
Does ceiling paint use the same coverage?
The calculator uses your coverage input for all paint. Check the ceiling paint label if it lists different coverage.