How Much Stain Do I Need?

This article clearly describes the formula for calculating how much stain you need to complete a given project. After describing different factors that might alter the amount of stain you need, it gives examples of common projects and the average amount of stain needed for each. 

Factors That Affect How Much Stain You Need

There are several factors that dictate how much wood you can expect to cover with a gallon of stain. Different products perform differently, and coverage can be significantly different even within brands.

The condition of the wood surface and its age are also factors that influence how much stain you can expect to use. 

Product

Different brands or products can offer vastly different amounts of coverage. The label on the can or container should list how many square feet you can coat with one gallon.

Many manufacturers make stain calculators available online so you can easily determine how much stain to purchase for your project, whether you’re covering decking, floors, or trim with stain. 

For example, if staining with Behr:

• To cover a 16′ x 16 deck’ in transparent wood stain, Behr’s stain calculator recommends purchasing two gallons of stain – one per coat.
• For semi-transparent and solid stain, three gallons is the recommended amount, assuming one and a half gallons per coat.
• Their decking protection product requires two coats, and covering the same area is expected to take three gallons per coat, for a total of six gallons. 

Cabot stain’s calculator differentiates between the amount of stain needed for wood that is new and/or smooth vs wood that is rough or aged. Here is another example if staining with Cabot:

• In the first case, they recommend 3 quarts per coat, for a total of one gallon and two quarts to cover the same 16′ x 16′ deck.
• In the case of rough or aged wood, more product is needed — about one gallon per coat, or two gallons total. 

For outdoor decks, always apply a deck sealant to your treated wood once done staining.

Wood Surface

Rough cut wood has more nooks and crannies than smooth wood, and it may take extra effort and product to get even coverage throughout each plank of wood.

For this reason, staining rough cut wood usually requires more stain than super smooth, sanded surfaces. 

Wood Age

Aged wood will generally take up more stain than new or ‘green wood’. You may go through your stain more quickly than expected if working with aged wood. 

End Grain

Whenever you are applying stain to end grain, it will soak up quite a bit more stain than other sections of wood. End grain is very porous, and difficult to get an even stain application.

If your wood piece has a log of sections of end grain, plan on utilizing more stain than normal.

Application Method

Stain is usually applied with a roller or a brush, but can also be sprayed on. When the stain is atomized by a spray gun, a significant amount of the material will float away before it reaches the surface of the stain.

If you choose to spray on stain, you will need to compensate for this material loss due to overspray.

After staining, make sure to apply a finisher like polyurethane to protect your wood.

Calculating Stain Amounts

In order to calculate how much stain you need for your next project, there are two measurements you need. First, you need to know the area of the object or structure you want to stain. The second measurement you need is the coverage of your chosen stain.

Calculating Area

Divide the surface to be stained into rectangles, and find the area of each rectangle. Add the results together to get the total surface area. The formula for finding the area of a rectangle is width multiplied by height. An eight foot high fence that is 50 feet long would have an area of 400 square feet. 

Stain Coverage

This should be clearly labeled on the container. The coverage tells you how many square feet you can expect to cover with one container. It also tells you whether the stain needs to be thinned.  

Once you have calculated the area, divide it by the coverage advertised on the container to find out how much you need to cover the area in one coat of stain. 

Example: 

Let’s say you need to cover 400 square feet of fence, but you want to stain both sides. This would be a total of 800 square feet that need to be covered with stain. 

If you want to apply more than one coat of stain, you will need to multiply the area by the number of coats. In the example above, if you’re planning on two coats of stain, you will need enough volume to cover 1600 square feet. 

• If the stain you choose advertises that it can cover 200 square feet per gallon, divide 1600 by 200 to get the volume of stain required to complete this project: eight gallons. 
• For the example cited here, the area divides neatly into whole gallons, but this isn’t always the case. If you get a fraction, it is usually best to round up to the nearest quart or whole gallon.

This process is very important to go through slowly. Whether calculating how much stain you need for hardwood floors or an intricate piece of furniture, it can be very confusing.

Units of Measurement for Stain

In the US, area measurements are usually described in square feet, and stain is usually measured in gallons. Stain is also sold by the quart (one-quarter of a gallon) and by the half-pint (one-sixteenth of a gallon).  Some stains are also available in pints. 

Outside the states, square meters are used to calculate area and liters represent the volume of stain. 

One gallon of stain usually covers between 200 and 300 square feet. 

The larger the area you need to stain, the more you would want to consider spraying the stain. Read my stain sprayer reviews to find the right one for your project.

When Does Stain Go Bad?

Under cool and dry storage conditions, stains can last about one year in the can once they’ve been opened. Unopened water-based stain has a shelf life of around two years. Unopened oil-based stain lasts even longer, up to about three years.

Stain that has gone bad changes texture, becoming glopping or stringy. Note that in pigmented stains, the large pigment particles often sink to the bottom if the can has been sitting on the shelf, and this is not an indication that the stain has degraded. A quick stir will redistribute the pigments throughout the suspension and make it ready to use. 

How Much Stain Do I Need For a Deck or Patio?

The average deck is 16 feet wide and 16 feet long, for a total of 256 square feet. Two coats of stain brings the total area to be covered up to 512 square feet. If you choose a stain that covers 200 square feet per gallon, you would need two gallons and a pint. 

However, most decks have railings that also need to be stained.

How Much Stain Do I Need For Deck Railings? 

For a structure with so much open space, railings and balusters actually require a significant amount of stain. This is because you need to stain all four sides of square balusters, as well as the top and underside of the rail. 

To calculate the square footage of each baluster, use a surface area calculator. You will need to know the length, width, and height of the baluster. Multiply the square footage per baluster by the total number of balusters, and add this to the square footage of your deck. 

Repeat the process for the top rail. 

How Much Stain Do I Need For a Dining Table?

The standard width for dining tables is 36 inches, or 3 feet. A table that seats eight diners is usually 80 inches long or nearly seven feet. This gives you an area of 21 square feet. Of course, you want to stain the top and bottom of the table, so you need to double that for a total of 42 square feet.

A quart of stain should be more than enough to cover a tabletop of this size. 

If you’re staining a wood like plywood, you might need more as it can soak up the stain a bit more rapidly.

Conclusion

The formula to calculate how much stain you need is area (expressed in square feet) divided by coverage (expressed in square feet per gallon). This will give you the volume of stain you need, expressed in gallons.