Finish Coverage Calculator
Estimate the oil, varnish, shellac, or lacquer a project needs from its area and coats, so you buy one can instead of running dry.
Buy the right amount of finish
Nothing stalls a project like running out of finish between coats — the new can never quite matches, and the wait breaks your rhythm. A quick estimate from surface area, coat count, and the finish's spread rate tells you what to buy before you start, whether that is a few ounces of oil for a box or a quart of varnish for a table.
Working out the whole project budget? Price the lumber with the Lumber Cost Estimator and size the boards with the Board Feet Calculator.
Frequently Asked Questions
How do I measure the surface area to finish?
Add up every face the finish will touch — the top, the sides and ends, the edges, and any interior surfaces that get coated — and convert to square feet. A simple box is quick to total; for turned or carved work, estimate generously. It is better to slightly over-measure the area than to run out of finish two coats in.
Why do different finishes cover different amounts?
Spread rate depends on the finish and how it goes on. Thin, penetrating products like wiping oils and wiping varnishes go a long way per gallon because you apply them in thin coats and wipe off the excess. Brushing varnish covers a bit less, and sprayed lacquer far less again because a lot is lost to overspray. The calculator uses a typical rate for each finish, which you can adjust for how you work.
How many coats should I plan for?
It depends on the finish and the look you want. Penetrating oils are often three or more thin coats; wiping varnish builds slowly over four to six; brushing varnish and polyurethane usually need two or three. Enter the number you actually intend to apply — the total volume scales directly with it, and the first coat on bare wood always drinks the most.
Should I buy exactly the amount shown?
Round up. Real coverage varies with how thickly you apply, how thirsty the wood is, and how much you lose to rags, brushes, and overspray, and the bare-wood first coat soaks in more than later ones. Buying the next size up costs little and saves a mid-project run to the store. And dispose of oily rags safely — spread them flat to dry or submerge them, because balled-up oily rags can self-heat and catch fire.
Estimates from typical spread rates. Real coverage varies with application, wood, and losses to rags and overspray. Round up when buying, and dispose of oily rags safely — they can self-heat.