Deck Stain Calculator: How Much Stain Do I Need?
The average amount of stain needed depends on the surface area.
Calculating precise square footage will require multiple formulas.
Our formula includes a spillage coefficient (because nobody works perfectly).
The average deck with railing and stairs will require between 3 and 4.5 gallons of stain.
How much stain do I need for my deck? Calculating the right number is key when considering the project as a whole. This calculator makes it simple to understand and calculate the total surface area of your deck, including railings and stairs. Let’s dive in.
How Much Stain Is Needed to Stain a Deck
Determining how much stain is required comes down to finding out the square footage you need to stain and comparing that to your stain’s coverage rate. While not all decks have railings and stairs, you can use the reference amounts below to approximate the stain required for your deck. The numbers below assume a stain that has a coverage rate of 200 square feet per gallon and factors in 3% spillage.
| Deck surface area (sq ft.) | Gallons of stain needed | Gallons of stain needed with railings | Gallons of stain needed with 4 stairs and railings |
|---|---|---|---|
| 100 | 1.1 | 1.3 | 1.4 |
| 200 | 2.1 | 2.3 | 2.4 |
| 300 | 3.1 | 3.3 | 3.4 |
| 400 | 4.2 | 4.3 | 4.4 |
| 500 | 5.2 | 5.3 | 5.5 |
Calculating How Much Stain You Need
Deck stain comes in different coverage amounts, but commonly, a gallon will cover between 150 and 225 square feet. You’ll need to measure your deck first to determine which stain to buy, so use the calculator below to come up with a number. Remember to multiply by the spillage coefficient at the end. A little waste is normal, as nobody works perfectly clean.
Stain needed (in gallons) = Deck area (square feet) x number of coats required / stain coverage rate (square feet per gallon) x 1.03 (spillage)
How to Measure Your Deck for Stain
Make sure you measure your deck's surface area accurately by double-checking all measurements. Don’t forget to add any side pieces, railings, or stairs to your calculations. Only once you have a final, accurate number can you purchase stain.
How to Measure the Deck’s Base Measurements
If your deck is a standard rectangle, consider yourself lucky, as these are the simplest decks to measure. Simply measure the length and width of the deck using a tape measure, and multiply the two numbers together to get your deck’s total square footage.
How to Measure Different Shapes
If your deck isn’t rectangular, don’t worry. You can break it down into individual sections and add them together later. Measure the largest rectangular section first, then break the rest into smaller pieces (usually triangles).
You’ll calculate these by multiplying the length of the triangle by the height, then dividing that number by two. This is how you calculate the area for all triangles, regardless of their shape.
How to Measure Stairs
Stairs are almost always rectangular, so measuring them is simple. Use the same length times width (height) formula you used to calculate the rectangular portion of your deck. You’d do this for each section of the stairs—the section you stand on is one measurement, as is the vertical riser section. If your stair has a lip, make sure to measure that too (if you plan on staining its underside).
How to Measure Railings
Calculating railing measurements is by far the most difficult part of this project. However, it isn’t impossible. The formula involves finding the height and length of the railing and the surface area of one of the posts, then adding them together.
However, there’s a trick. Wrap a measuring tape around a post. That is now your width measurement, as an unrolled post becomes a rectangle. Multiply that by the post's height, and you now have the surface area for one post. Simply add the number of posts, multiply by their area per post, and add the railing length and height.
Who to Hire to Stain Your Deck
A local deck staining pro is who to call to stain your deck for you. These pros have the expertise and tools required to complete the job to the highest standard. If you choose to go the DIY route, you can lean on a local pro to assist with any questions you might have about measurements, stains, and finishes.
Frequently Asked Questions
Sealing a deck can cost between $550 and $1,400, averaging around $960. To be more granular, costs can be between $0.75 and $4 per square foot. Keeping costs low can be difficult, but homeowners can save by doing prep work themselves, applying thin coats, only working during good weather, and DIYing as much work as possible.
There are more pros than cons when staining a deck. Deck stain is more affordable than paint, it protects the wood and allows the natural textures to shine through, and it can revive the appearance of your home. However, deck stain also requires prep work (sometimes days or more), carries more upkeep than a painted deck, and can fade over time if not cared for.
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