Deck Stain Calculator

Use the calculator below to estimate how much material you’ll need to paint or stain a deck.

Deck Size
Paint or Stain Details

Stain Estimate:

Total Stain Needed:
Stain Needed per Coat:
Total Square Footage:
Learn how we calculated this below

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How to Estimate Paint or Stain for a Deck

Over time, wooden decks can become weathered and dull, and they’ll need a fresh coat of paint or stain to restore their beauty and protection. Stain does more than simply make your deck look beautiful; it also helps protect your deck from the elements and UV rays. Stain ideally needs to be reapplied every other year, while paint can last three to five years before you need to repaint.

Before you start the staining process, you need to estimate how much paint or stain you’ll need to complete the project.

There are a few things you need to do to estimate stain for a deck.

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Step One: Measure the Deck

Measure the length and width of the deck, then multiply these measurements together to find the total square footage. Repeat this process for each rectangular section of the deck.

If you’re finishing the stairs, then you’ll need to measure the width and depth of each tread, and multiply them together to find the square footage. Then multiply this by the number of steps. Repeat this for each riser on the stairs as well.

If you’re finishing the railing, then you’ll need to measure the length and height of the railing, and multiply together to approximate the square footage. The railing square footage will be a rough estimate, but since the balusters need to be coated on four sides, this should be reasonably close.

Remember that many decks have additional areas that may require stain. This may include the trim around the edge, posts or poles, the stringers on the sides of the stairs, as well as features like built-in benches. Be sure to measure each of these areas as well to ensure you have enough stain for the entire project.

Add all of these square footage measurements together to estimate the total square footage. Most deck stains can cover between 150 and 300 sq. ft. per gallon.

If your deck is older and extremely weathered or if it’s very new and has never been stained before, you may need additional stain. If you are getting close to the top range of what a gallon can cover, make sure that you purchase an additional gallon.

Step Two: Note the Type of Wood

The type of wood you’re trying to finish will determine how much stain you need to cover it fully. Softwoods, such as pine or cedar, will absorb more than hardwoods, such as teak.

A new deck constructed using new, unfinished lumber will also absorb more finish than one that has previously been stained. Keep in mind that prior to staining, the deck should be pressure washed, which will remove any old and loose stain. Don’t count on there being a solid coat of stain in place that you will be covering over.

The age of the deck will also play a role. Significant weathering causes the grain of the wood to open and will require much more stain to get full coverage than wood that is not heavily weathered.

If there are any sections of the decking that are beyond repair, then it’s best to replace them before you apply the new finish so they blend with the rest of the deck. Learn more about how much it costs to repair a deck.

Step Three: Choose a Stain Product

Each type of paint or stain varies in how much square footage it will cover per coat. Check the can to find the coverage rate for the specific product you intend to use.

Typically, one gallon of paint or stain covers around 175 square feet of decking.

Keep in mind that if you are using a solid stain or a paint, and you have a cedar or redwood deck, you may need to prime it first. Both cedar and redwood will discolor paint. This is known as cedar bleed, and a good primer will stop it from discoloring the paint.

Step Four: Calculate the Amount of Stain Needed

Once you have the measurements of the deck and the coverage rate for the product you’re using, it’s time to calculate how much stain you need.

Start by dividing the square footage of the deck from step one by the coverage rate of the product you’re using.

Then, multiply that by the number of coats you want to apply to get the total number of gallons of stain needed. Typically, two coats are required to get a good finish, but keep in mind that very light or dark colors may require an additional coat.

This is particularly true if you are switching deck stain colors and moving from light to dark or dark to light. Stains have different amounts of coverage, from semi-translucent to opaque.

Therefore, the rate that they can cover will also differ. Opaque stains may cover more completely in one coat than a semi-translucent stain.

You should also consider adding an extra 10% of additional stain to account for spillage, drips, waste, etc.

In general, refreshing a deck with a few coats of stain is a cost-effective way to restore its beauty and add a layer of protection.

You might also be interested in calculating the amount of stain needed for a fence.