Paint Calculator
Estimate paint for rooms, single walls, and measured surfaces with coats, coverage, openings, waste, and cost
Longest room dimension.
Shortest room dimension.
Floor to ceiling height.
Horizontal wall measurement.
Vertical wall measurement.
Use this when area is already measured.
Typical interior door area is subtracted.
Typical window area is subtracted.
Extra cabinets, large openings, or skipped areas.
Most projects use one primer plus one or two finish coats.
Check the paint label and adjust for surface texture.
Adds buffer for touch-ups, roller loss, and rough surfaces.
Optional material cost per gallon or liter.
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How This Paint Calculator Works
Estimate painted area first, then apply coats, waste, coverage, and paint unit size.
Measure the surface
Room mode estimates all four walls from perimeter x height. Wall mode handles one wall, and surface mode starts from a known square-foot or square-meter area.
Subtract openings
Door and window counts remove typical opening areas. Add custom opening area for cabinets, large pass-throughs, or surfaces you will skip.
Apply paint coverage
The calculator multiplies by coats, adds waste, then divides by your paint coverage rate to estimate gallons or liters.
Paint Calculator Examples
Quick reference estimates for common interior paint projects.
Two coats, no ceiling, one door, two windows, and 10% waste at 350 sq ft/gal.
Two coats and no waste at 10 sq m/L coverage.
Two coats and 10% waste at 350 sq ft/gal.
Paint Calculator FAQ
Practical answers for paint coverage, coats, primer, waste, and buying cans.
How much does one gallon of paint cover?
A common planning estimate is about 350 square feet per gallon for smooth interior walls. Rough surfaces, dark color changes, porous drywall, and sprayed applications can use more paint.
Should I include the ceiling?
Include the ceiling when it will be painted with the same paint. Leave it unchecked when estimating only the walls or when the ceiling uses a separate product.
How much paint should I add for waste?
A 5% to 10% allowance is common for touch-ups, roller loss, color changes, and uneven surfaces. Use more for textured walls, primer-heavy projects, or uncertain measurements.
Does this estimate include primer?
No. This calculator estimates finish paint. Primer often has different coverage, so estimate primer separately if you are painting new drywall, stains, raw wood, or a major color change.
Should I buy exactly the calculated amount?
Treat the amount as a planning estimate and round up to available can sizes. Keeping a small remainder is useful for touch-ups and batch consistency.