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Yardwork

Paint Calculator

Free paint calculator: enter your wall size, openings, number of coats, and the coverage on your paint label to see how many gallons or liters of paint you need.

  • Free, no signup
  • Formula shown
  • Rounds up to whole units
  • Updated October 2026

Common rooms (8 ft walls)

Walls
Units
Measure by

Add up every wall you'll paint.

Doors, windows, built-ins.

Paint

Use the low end of the label's range.

Paint for 2 coats

1.83gallons

Buy

2 × 1 gallon

2 gal total

Paintable area

366 ft²

after 50 ft² openings

Total wall area
416 ft²
Area × coats
732 ft²
Same amount in liters
6.93 L

Coverage is not guaranteed. Texture, porosity, color changes, and application method all affect how far paint goes.

2 × 1-gallon cans

AnswerPainting 366 sq ft with 2 coats at 400 sq ft per gallon takes 1.83 gallons, so buy 2 1-gallon cans (2 gallons).

How to use this paint calculator

  1. Choose feet and gallons or meters and liters. Switching converts the numbers already entered.
  2. Enter the total length of the walls you'll paint and the wall height. Or switch to Total area if you already know the square footage.
  3. Enter the area of doors, windows, and anything else you won't paint.
  4. Enter the number of coats.
  5. Enter the coverage from your paint's label. If the label gives a range, the low end is the cautious choice. Rough, porous, or patched surfaces use more paint.
  6. Pick the container size you plan to buy.

How to calculate paint: the formula, shown

Paint needed = paintable area × number of coats ÷ coverage per gallon (or per liter). The paintable area is the wall area minus anything you won't paint. The coverage figure must come from your paint's label or data sheet: it varies between products, and the manufacturer states the conditions behind it.

Default example. The four walls of a 12 × 14 ft room (52 ft of wall), 8 ft high, 50 ft² of openings, 2 coats, and 400 ft² per gallon. That coverage is the low end of the 400–450 ft² per gallon spread rate Benjamin Moore publishes for Regal Select Eggshell (N549). It is not a figure for paint in general. Change the inputs above and the result panel recalculates; this worked example always shows the default.

Default example arithmetic
Wall area   = 52 ft × 8 ft = 416 ft²
Paintable   = 416 − 50 = 366 ft²
Paint       = 366 ft² × 2 coats ÷ 400 ft²/gal = 1.83 gal
Containers  = 1.83 ÷ 1 gal = 1.83 → 2 × 1-gallon can
In liters   = 1.83 gal × 3.785411784 = 6.927 L

How much paint for common room sizes

Paint for the four walls of common room sizes with 8 ft walls, 2 coats, and no openings deducted, computed with the same formula as the calculator. Coverage is 400 ft² per gallon: the low end of the range Benjamin Moore publishes for Regal Select Eggshell (N549), used here only as an example. It is not a figure for paint in general. Enter your own paint's label coverage above for your answer.

Paint for common room sizes
RoomWall areaGallons (2 coats)1-gallon cansQuarts instead
10 × 10 ft320 ft²1.627
10 × 12 ft352 ft²1.7628
12 × 12 ft384 ft²1.9228
12 × 14 ft416 ft²2.0839
14 × 16 ft480 ft²2.4310
16 × 20 ft576 ft²2.88312
20 × 20 ft640 ft²3.2413

How much paint do I need to buy?

For the default room, buy 2 1-gallon cans (1.83 gallons needed).

  • Mixing container sizes: if the requirement is just over a whole gallon, a quart may cover the remainder for less. Run the calculator with quarts to see how many quarts would be needed.
  • Primer: primer is a separate product with its own coverage. Run the calculator again with the primer's label coverage and one coat.
  • Ceilings and trim: calculate them separately when they use a different paint.
  • Same batch: buying all the paint for one wall color at once helps keep the color consistent.

Tips for estimating paint

  • A standard way to get total wall length is the room's perimeter: 2 × (length + width).
  • Gable walls and sloped ceilings are triangles or trapezoids. See measuring irregular areas.
  • Large color changes and new drywall often need more coats or a primer. The label or retailer can advise.
  • Painting new drywall? Size the job first with the drywall calculator.
  • Keep the label or data sheet. It lists coverage, recoat time, and the film thickness the coverage assumes.

Paint calculator FAQ

How much paint do I need for a room?

Multiply the total wall length by the wall height, subtract doors and windows, and multiply by the number of coats. Divide that by the coverage on your paint's label, then round up to whole containers.

How much paint for a 12 x 14 room with 8 foot walls?

The four walls total 416 sq ft. Excluding 50 sq ft of openings leaves 366 sq ft. Two coats at 400 sq ft per gallon need 1.83 gallons, so 2 gallons. Your result depends on your paint's stated coverage.

How many square feet does a gallon of paint cover?

It depends on the product and the surface, so use the figure on your label. For example, Benjamin Moore publishes 400–450 sq ft per gallon for Regal Select Eggshell (N549), depending on surface texture and porosity. Other products state different figures.

Why doesn't the calculator use a standard coverage number?

There isn't one. Coverage varies by product, sheen, color, surface, and application, and manufacturers state their own figures. A built-in constant could leave you short, so the calculator asks for the number from your label.

Is the label's coverage guaranteed?

No. Label coverage assumes a particular film thickness and surface. Rough, porous, or patched surfaces, dark-to-light color changes, and spraying can all use more paint. Using the low end of the label's range is the cautious choice.

Should I subtract doors and windows?

Yes, if you won't paint them. Measure each opening (width × height) and add them up. For a small room with few openings, some painters skip the deduction to leave a margin.

How do I calculate paint in liters?

Switch the units to meters and liters, and enter coverage in square meters per liter from the label. The result shows liters, with the US-gallon equivalent alongside (1 US gallon = 3.785411784 liters).

How many coats of paint do I need?

That depends on the paint, the surface, and the color change. Check the manufacturer's instructions. Enter the number of coats you plan, and the calculator multiplies the area by it.

Calculators

  • Drywall Calculator — Drywall sheet count for walls and ceilings from room dimensions or total area, minus openings, by sheet size.
  • Deck Calculator — Decking board count from deck size, actual board width, gap, and board length, with the cutting assumptions shown.
  • Roof Pitch Calculator — Pitch as x/12, roof angle in degrees, slope percentage, and the sloped length for a given horizontal run.

Guides

Sources