Wood Finish Coverage Calculator

How This Tool Works

This wood finish coverage calculator determines how much finish you need based on three key factors: surface area (in square feet), finish type (polyurethane, Danish oil, tung oil, etc.), and number of coats. Different finishes have significantly different coverage rates - thin penetrating oils like Danish oil cover more area per liter (18 sq ft per liter per coat) than thick protective finishes like polyurethane (12 sq ft per liter per coat).

The calculator accounts for the fact that coverage varies based on wood porosity (hardwoods absorb less than softwoods), application method (brush vs. rag), and surface preparation (smooth vs. rough). It multiplies surface area by number of coats and divides by the coverage rate for your chosen finish type. Always add 10-20% extra to the calculated amount to account for waste, spills, touch-ups, and future maintenance. This ensures you don\'t run out mid-project and have extra for future repairs.

Coverage Rates by Finish Type

• Polyurethane: ~12 sq ft per liter per coat (thick, protective finish)
• Danish Oil: ~18 sq ft per liter per coat (penetrating oil, thin coats)
• Tung Oil: ~15 sq ft per liter per coat (natural finish, multiple thin coats)
• Linseed Oil: ~20 sq ft per liter per coat (penetrating, thin application)
• Varnish: ~14 sq ft per liter per coat (similar to polyurethane)
• Lacquer: ~16 sq ft per liter per coat (fast-drying, thin coats)

Note: Coverage rates are approximate and vary based on wood type, porosity, application method, and surface preparation. Always check manufacturer specifications.

FAQ

• How do I calculate surface area?
  For flat surfaces: Length (ft) × Width (ft). For multiple surfaces (like a table top and legs), calculate each separately and add them together. For complex shapes, break them into simple rectangles and add the areas. Don't forget to include all surfaces that will be finished - tops, sides, edges, and any hidden areas if you're finishing those too. Measure carefully for accurate calculations.
• How many coats do I need?
  Most wood finishes require 2-3 coats for proper protection. Polyurethane typically needs 2-3 coats, Danish oil needs 2-4 thin coats, penetrating oils may need 3-5 coats, and varnish needs 2-3 coats. Always follow manufacturer recommendations on the product label. More coats provide better protection but use more finish. Sand lightly between coats for best results.
• Why do coverage rates vary?
  Coverage depends on several factors: wood porosity (hardwoods like oak absorb less than softwoods like pine), application method (brush applies thicker than rag, reducing coverage), finish type (thick finishes like polyurethane cover less than thin oils), and surface preparation (rough or porous wood absorbs more finish). Always add 10-20% extra for waste, spills, and touch-ups to account for these variables.
• Should I buy extra finish?
  Yes, always buy 10-20% more than calculated to account for waste, spills, touch-ups, drips, and future maintenance. It's much better to have extra than to run out mid-project and risk color or finish inconsistencies. Extra finish can also be used for future repairs or touch-ups. Most finishes store well if sealed properly.
• Do different wood types affect coverage?
  Yes, significantly. Porous woods like pine, fir, and cedar absorb much more finish (may need 20-30% more) than dense hardwoods like oak, maple, or cherry. Rough-sawn wood absorbs more than smooth-sanded wood. End grain absorbs much more than face grain. Adjust your calculations accordingly - if working with very porous wood, add 20-30% to your estimate rather than the standard 10-20%.
• Can I mix different finish types?
  Generally, no. Different finish types (oil-based vs. water-based, polyurethane vs. oil) are not compatible and should not be mixed. Stick with one finish type for the entire project. However, you can use compatible products together (like stain followed by polyurethane, or Danish oil followed by polyurethane after proper curing). Always check product compatibility before mixing.