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About this tool
Litres of wood stain, sealer or varnish for a surface area, adjusted for texture, wood porosity, coats and wastage.
This calculator converts a wood surface area into the litres of stain, oil, sealer or varnish the job actually needs. It starts from the product's spreading rate in square metres per litre per coat, divides it by a texture factor and a porosity factor — rough-sawn timber and open-grained softwood both have far more real surface than their measured area — and loads the first coat on bare wood by 1.3× because raw grain drinks it. Furniture makers, decorators and DIY finishers use it to buy the right tin size instead of running out halfway through the second coat.
Open Wood Stain Quantity Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Texture and porosity factors turn the tin's best-case spreading rate into what you will actually get.
Shows the heavier first coat separately from the later ones, so partial jobs can be costed too.
Rounds up to 0.25 L through 20 L tins and reports the leftover, not just a raw litre figure.
Roughly 0.11 litres per square metre per coat on smooth, planed timber, since typical interior stains cover 8–10 m² per litre. Rough-sawn or weathered wood can drop to 3–4 m² per litre, so the same area may need three times as much.
Yes — bare wood absorbs roughly 25–35% more on the first coat because the open grain soaks it up before any film forms. This calculator applies a 1.3× loading to coat one on bare timber and leaves later coats at the base rate.
Two coats is standard for pigmented stains and polyurethane, three for penetrating oils like Danish or teak oil, and one for a sanding sealer under a topcoat. More coats deepen the colour rather than adding protection, so the topcoat is what determines durability.
Divide square feet per US gallon by 40.7 to get square metres per litre. A stain quoted at 400 sq ft per gallon is about 9.8 m² per litre; one quoted at 150 sq ft per gallon, typical for rough exterior timber, is only about 3.7 m² per litre.
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