Floors & Walls

Paint Calculator

Estimate finish paint, whole containers and a separate primer quantity.

Units

Your measurements

Results update as you type.

Example shown — use your own measurements.

Enter the area and matching paint volume stated on the finish-paint label.

For 400 ft² per US gallon, enter 400 ft² above and 1 US gal here.

Extra options & cost (optional)

Applied once. Choose an allowance for your project; zero adds no extra material.

Fractions and number formats

Use decimals (12.5), fractions (12 1/2 or 12-1/2), or explicit lengths (12ft 6in, 12′ 6″, 25 mm). A comma followed by one or two digits is a decimal comma: 12,5 = 12.5. Grouped commas mean thousands: 1,200 = 1200. Use a decimal point for ambiguous values. Scientific notation is not accepted.

Enter your measurements

Results update as you type.

About this calculator

Estimate finish paint, whole containers and a separate primer quantity. Enter your measurements and check the worked example below. Product quantities use the label information you supply.

How to measure

  • Measure the actual usable surface or internal space, using the field labels for the selected mode.
  • Keep openings and excluded areas separate so they are subtracted once.
  • Recheck units and label coverage before ordering.

How to use this calculator

  1. Choose known paintable area or room dimensions; select whether to include the ceiling.
  2. Subtract the total door/window area once and enter the finish-coat count.
  3. Enter both the coverage area and matching paint volume from the finish-paint label.
  4. Add a container size for whole-container purchasing; if primer is enabled, enter its own coats and label coverage.

Formula

Room wall area = 2 × (length + width) × height; optional ceiling = length × width

Net area = gross area − openings

Paint volume = net area × coats × allowance factor × label volume / label coverage area; containers round up

Primer uses its own coats and label coverage; it is not included in finish paint cost

Assumptions

  • Room mode treats the walls as a rectangular perimeter times one height, with the ceiling added only when selected.
  • Finish paint and primer use their own stated label coverage and coat counts.
  • The extra allowance is applied once; finish-container purchases round up and primer is not priced.

Common mistakes

  • Applying the same allowance in both measurements and the extra-material field.
  • Entering coverage or yield from a different product or measurement basis.
  • Treating a quantity estimate as an installation or structural approval.

Worked example

Try it: press “Load example” above the form.

1,000 ft² × 2 coats ÷ 400 ft² per US gallon = 5 US gallons of finish paint.

Limitations

Label coverage varies with substrate, porosity, color change and application. Openings are area deductions only. Primer uses its own label rate and is not priced here. No preparation or labor estimate is included.

Frequently asked questions

How do I enter a coverage such as 400 square feet per gallon?

Enter 400 ft² as label coverage area and 1 US gallon as its matching paint volume. Use the exact labelled gallon or litre basis, coat count and product; US and imperial gallons differ.

What does the worked example show?

1,000 ft² × 2 coats ÷ 400 ft² per US gallon = 5 US gallons of finish paint.

Is primer included in the finish-paint total?

No. Enable the separate primer estimate and enter its own coats and label coverage. Finish paint and primer are displayed separately, and primer is not priced by the finish-container price.

What changes practical coverage on a real surface?

Label coverage varies with substrate, porosity, color change and application. Openings are area deductions only. Primer uses its own label rate and is not priced here. No preparation or labor estimate is included.

Reviewed by Codex AI editorial agent (Editorial, 2026-11-12).

Sources

Sources explain the methods and any named product presets. Check your product label where coverage, yield or density differs.

  • NIST: Revised Unit Conversion Factors
  • Defined geometric and purchase-quantity model

    Formulae on this page define the arithmetic model. Worked examples are illustrative, not product or installation recommendations.

Calculation documentation · Updated 2026-11-11 · Version 1.6.4. Estimates are planning aids. Confirm quantities, coverage and prices with your supplier before purchasing. Found an error? Report it.

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