Wood finish coverage calculator

How to use this calculator

The amount of finish a project needs is surface area × number of coats ÷ coverage. The calculator works out the area of the top from its length and width, doubles it if you finish the underside too, and adds a percentage for edges, legs, aprons and other parts. That total is multiplied by the number of coats and divided by the coverage figure from the product label.

For example, a 6 × 3 foot tabletop finished on both faces is 36 square feet, plus 20% for edges and the base is 43.2 square feet per coat. Three coats is 129.6 square feet. At a label coverage of 450 square feet per gallon that is about 0.29 gallon, a little over one quart.

The 450 square feet per gallon default is only a placeholder: coverage differs a lot between oils, wiping varnishes, brushing polyurethanes and waterborne finishes, and it is always printed on the can or the product data sheet. Enter the manufacturer's figure and pick the matching unit; the calculator converts square meters per liter to square feet per gallon (1 m²/L is about 40.7 sq ft/gal). Label coverage assumes a typical film on a sealed surface. Bare wood absorbs more on the first coat, end grain absorbs much more, and thinned wiping coats spread further, so treat the answer as a minimum and round up to the next can size.