Paint Calculator
Multiple rooms, separate wall and ceiling coatings, primer and optimized cans.
| Product | Selected container mix | Paint purchased | Paint cost |
|---|---|---|---|
| Wall paint | 2 × 1 gal + 2 × 0.25 gal | 2.5 gal | — |
How it works
Wall and ceiling areas are summed across every included room and measured zone. Each product then uses its own coverage, coats and allowance; primer is calculated over the complete prepared surface.
Container sizes are optimized separately because wall paint, ceiling paint and primer are different products. When all entered sizes have prices, the lowest-cost sufficient mix wins. Otherwise the calculator minimizes purchased volume and then container count.
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How the Paint Calculator works
This US paint calculator combines up to three rooms and measured square-foot zones, keeps wall paint, ceiling paint and primer separate, and selects a gallon, five-gallon and quart purchase mix from the sizes and prices entered.
Start with the surfaces, not the floor square footage
Wall area is room perimeter times ceiling height, less openings. Each ceiling is length times width and is included only when selected. A quick floor-area multiplier misses ceiling height and openings, while the room model produces an auditable quantity without asking for every wall separately.
Second and third rooms are added before container rounding, so a partial gallon from one room can cover the next. Direct wall and ceiling fields handle accent walls, halls or irregular measured zones without forcing them into a rectangular-room model.
Coverage is an input, not a universal promise
The 400 ft² per gallon default is a planning value for one coat. Paint line, sheen, application method, texture, porosity and color change all move actual coverage. Replace the default with the range on the exact product label.
Bare drywall or masonry and strong dark-to-light changes may consume more or require primer. Primer has its own coverage, coats, package sizes and prices instead of being treated as an unexplained increase in finish paint.
Optimize real container sizes
Wall paint, separate ceiling paint and primer each accept three available can sizes. When all sizes for a product have positive prices, the least expensive sufficient combination wins. With incomplete prices, the optimizer minimizes purchased gallons and then can count.
The products remain separate because primer surplus cannot replace finish paint and a ceiling coating may differ from the wall line. The table exposes every selected can combination, purchased volume and cost instead of returning only an abstract gallon total.
FAQ
How much paint does a 16 × 13 ft room need? expand_more
At 9 ft high, the walls total 522 ft². Subtract 54 ft² of doors and windows to get 468 ft². At 400 ft² per gallon and two coats, the estimate is 2.34 gallons for the walls.
Does the calculator include two coats? expand_more
The default is two coats, and the field is editable. Coverage is stated per coat, so changing from two to three coats increases the gallons by half.
Should I round gallons up? expand_more
Enter up to three can sizes sold for the selected product. The calculator finds a sufficient combination for the complete project and shows purchased gallons and surplus, so it does not round every room independently.
Can wall and ceiling paint use different coverage? expand_more
Yes. Choose a separate ceiling product and enter its coverage, coat count, sizes and prices. If the same coating is used everywhere, combine the ceiling with the wall product so its containers are optimized together.
How much primer does the project need? expand_more
Enable primer to apply its editable one-coat coverage to all selected wall and ceiling square footage. Primer containers and cost are optimized independently from finish paint.