WoodTools

Wood Finish Calculator

Buy finish once, not twice. Enter your surface, the number of coats and the product coverage to get the exact litres for varnish, paint, stain or oil.

A roller applying varnish to a wood surface with a varnish can nearby. 2 coats · 10 m²/l 1 L varnish
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Workshop AI assistant

Describe the piece you want to build and get a complete plan: dimensions, cut list, materials, cost, steps, tools and time.

Workshop assistant

Describe the piece you want to build and get a complete plan: dimensions, cut list, materials, cost, steps, tools and time.

AI-generated results are indicative. Verify dimensions, loads and local codes before building.

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How it works

  1. 1

    Choose the finish type (varnish, paint, stain, oil).

  2. 2

    Enter length and width of one surface and the number of identical surfaces.

  3. 3

    Set the number of coats and the product coverage in m²/litre.

  4. 4

    Calculate to get the net litres, recommended quantity with margin and can size.

Formula

Total area = length × width × number of surfaces. Net litres = total area × coats / coverage. Recommended = net litres × (1 + margin). The tool rounds up to the nearest commercial can size.

Practical tips

  • Coverage on the can assumes a smooth sanded surface; rough or end-grain wood absorbs far more.

  • Varnish: 2–3 coats minimum. Oil: apply generously, then wipe off the excess.

  • Sand between coats and the coverage improves with every pass.

  • Stain is often sold thinner — check whether your quantity is in litres or ml.

Common mistakes

  • Using the surface of the front face only and forgetting sides and edges.

  • Ignoring the higher absorption of end grain and raw wood.

  • Applying the first coat with the same coverage as the last.

  • Buying a can size just below the calculated quantity.

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Disclaimer

These results are indicative only. Always verify against local building codes, standards and professional advice before building.

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Frequently asked questions

Why does the first coat need more product?
Raw wood absorbs aggressively, especially end grain and open-pored species like oak. A first coat can use up to 50% more product than a top coat.
What coverage should I use?
Read the can: most varnishes cover 8–12 m²/l, paints 8–12 m²/l, stains 8–15 m²/l and oils 10–18 m²/l per coat.
How do I know how many coats I need?
Varnish and paint generally need 2–3 coats. Oil and stain often one generous application, repeated only where needed.
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