The job sheet above calculates wall finish paint, using your measurements and the coverage on your chosen paint’s label. Enter each wall as width × height, with an optional quantity for identical rectangles. Deduct only openings that will not receive that finish. Keep ceilings, doors, trim and primer on separate sheets when they need different products or coverage rates.

Follow the area through to the cans

The method is net wall area × finish coats ÷ coverage per unit of paint. A coverage range produces two quantities: the higher spread rate gives the lower quantity, and the lower spread rate gives the higher quantity. The tool then applies your separate extra allowance and rounds each can-size comparison up to whole containers.

For the starting example, four 10 × 8-foot walls give 320 square feet. Deducting a 2.5 × 8-foot opening leaves 300 square feet. Two coats at 300 square feet per US gallon need 2 US gallons before any extra allowance. That is arithmetic for those inputs, not a claim that a particular paint achieves that coverage on your wall.

If the same 600 square feet of coated area uses a 250–400 square-foot-per-gallon range, the paint quantity is 1.5–2.4 gallons before allowance. Using only one-gallon cans means two to three cans. A row comparing five-gallon pails does not mean a pail is economical: the table shows quantity and surplus, without assuming prices or a mixed-size optimum.

Take coverage and coats from the exact label

Behr’s interior quantity guidance gives 250–400 square feet per gallon for one coat of its named ULTRA and PREMIUM PLUS interior products. It also directs readers to the product label for paint-specific differences. That range is an example of why a single universal coverage number is inadequate; the calculator does not load it as a verified recommendation for your paint.

Surface condition, texture, porosity and the color change can affect the job. A paint-and-primer name does not combine every required preparation coat into your finish-paint quantity. Confirm the specified preparation and coats, then use the chosen product’s coverage range. An extra reserve is your planning choice, separate from using a conservative spread rate.

Keep the sheet with the project

CSV export records the inputs, units, quantities and uniform can-size plans. Printing includes those inputs and results. Changing the unit selector changes the system expected for your next entries; it does not convert the numbers already in the fields. In metric mode, use meters for rectangles, square meters per liter for coverage and liters for can sizes.

The calculation does not model a vaulted ceiling, sloped wall, spray-transfer efficiency or overlapping deductions automatically. Divide the relevant surface into measured, non-overlapping shapes, or keep an irregular section separate until you can measure it. The tool cannot establish preparation quality or a one-coat outcome.

Source and method

Desk research, checked October 15, 2026. The original worksheet exposes geometric area, coverage assumptions and whole-container rounding; it does not report hands-on paint testing.