Whether you are refinishing a hardwood floor, sealing a table top or protecting a deck, the amount of finish you need depends on the area, the coverage per gallon of the product and the number of coats. This calculator also shows how long the work takes, because the waiting time between coats is often what decides the schedule.
Typical coverage per coat
| Product | Coverage |
|---|---|
| Oil-based polyurethane | about 500 sq ft per gallon |
| Water-based polyurethane | about 400 to 500 sq ft per gallon |
| Varnish | about 400 sq ft per gallon |
| Penetrating oil | about 300 to 400 sq ft per gallon |
| Wood stain | about 200 to 400 sq ft per gallon |
Raw or porous wood absorbs more on the first coat, and a rough deck can take twice as much as a sanded floor. Always check the label of your product.
How the calculation works
- Finish needed = area × number of coats ÷ coverage
- Cans = finish needed ÷ can size, rounded up
- Minimum time = (coats − 1) × hours between coats
Example
Three coats of oil-based polyurethane on a 300 sq ft floor need 300 × 3 ÷ 500 = 1.8 gallons, so 2 gallon cans. With 24 hours between coats, the last coat goes on two days after the first, and you should wait several more days before moving furniture back.
How many coats?
- Floors: 3 coats of oil-based or 3 to 4 coats of water-based polyurethane, which goes on thinner.
- Table tops and counters: 3 coats or more.
- Furniture and trim: 2 coats is often enough.
- Oils: 2 to 3 thin coats, wiping off the excess.
Tips for a good finish
- Sand lightly with fine abrasive (220 grit or a screen for floors) between coats and remove all dust.
- Apply thin coats: thick coats dry slowly, stay soft and can wrinkle.
- Ventilate well, especially with oil-based products.
- Drying times on the can assume about 70 °F and 50% humidity; cold or damp weather slows everything down.
- Rags soaked with oil-based finishes can catch fire by themselves: lay them flat to dry outdoors or keep them in water in a closed metal can.