Paint Calculator Widget

Add a paint calculator to a DIY, decorating or paint-shop site. Readers enter the wall length and height, doors, windows, coats and the coverage printed on the tin, and see how much paint to buy in cans.

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<iframe src="https://a2z.tools/embed/w/paint-calculator" title="Paint Calculator by A2Z Tools" width="100%" height="810" style="border:0;width:100%" loading="lazy" allow="clipboard-write"></iframe>

A plain iframe. Works everywhere, including site builders that strip scripts. Adjust height if your content needs more room.

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How it works

The method matches the A2Z Paint Calculator: wall area less openings, times the number of coats, divided by the coverage per litre or gallon. The widget adds door and window sizes and then rounds the amount up to whole cans - 1, 2.5, 5 and 10 litres, or quarts, gallons and 5-gallon pails - choosing the mix that leaves the least paint over, then the fewest cans.

Calculation method

  • Wall area = total wall length x height
  • Paintable area = wall area - doors x area per door - windows x area per window (defaults 1.9 and 1.5 m2, or 20 and 15 sq ft)
  • Paint = paintable area x coats / coverage per litre or gallon
  • Cans (1, 2.5, 5, 10 L or 1 quart, 1 gal, 5 gal): the combination with the smallest total volume that is at least the paint needed, then the fewest cans
  • Paint needed and left over are shown to 2 decimals; can counts are whole numbers

Worked examples

Bedroom, metric

Inputs: Walls 16 m long x 2.5 m high, 1 door, 2 windows, 2 coats, coverage 10 m2 per litre

Result: Paint needed 7.02 L; buy 1 x 5 L + 1 x 2.5 L (7.5 L), 0.48 L left over

40 m2 of wall less 1.9 m2 of door and 3.0 m2 of windows is 35.1 m2; two coats at 10 m2 per litre need 7.02 L.

Living room, imperial

Inputs: Walls 52 ft x 8 ft, 1 door, 2 windows, 2 coats, 350 sq ft per gallon

Result: Paint needed 2.09 gal; buy 2 x 1 gal + 1 x 1 quart (2.25 gal)

416 sq ft less 50 sq ft of openings is 366 sq ft; 732 sq ft of coats / 350 = 2.09 gallons, so two gallons and a quart.

Limitations

  • Can sizes are fixed at 1, 2.5, 5 and 10 litres or quart, gallon and 5-gallon; brands that sell 0.75 L, 3 L or 4 L tins are not matched.
  • Primer, mist coats on new plaster and trim, skirting or door paint are not included.
  • Every door and every window uses one average size; enter unusual openings such as patio doors by adjusting the area per door.

Where publishers use it

  • Paint and hardware shops' product pages
  • Interior-design and DIY blogs
  • Painting contractors' quote pages
  • Landlords planning a repaint between tenants

Questions

What coverage should I use?

Use the spreading rate printed on the tin or the manufacturer's data sheet for your exact product, per coat. Rough, porous or new plaster surfaces absorb more, so use the lower end of any range given.

Why does it suggest 5 L + 2.5 L rather than a 10 L tub?

7.02 L is needed in the default room. 5 + 2.5 = 7.5 L leaves 0.48 L over, while a 10 L tub leaves almost 3 L, so the widget picks the mix with the least left over and only then the fewest cans.

How do I get the total wall length?

Add the widths of every wall you will paint - for a rectangular room, twice the length plus twice the width.

Does it include the ceiling?

No. Work out the ceiling separately by entering its length as the wall length and its width as the height.

Why might I need more?

A strong colour change, a dark colour over light, or a first coat on bare plaster often needs an extra coat or a primer.

Cite or recommend this tool

If you reference this tool in an article, course or documentation, these formats are ready to copy. They are optional - nothing is added to your site unless you paste it.

A2Z Tools Paint Calculator
https://a2z.tools/paint-calculator

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