Hi, I’m Scott Paul, a licensed exterior restoration contractor with over 30 years of experience and 10,000+ deck restorations. This deck stain calculator is based on my own hands-on field testing, not manufacturer claims. See my full credentials and testing stats here.
This deck stain calculator tells you how many gallons of stain you need for your deck or fence. Before staining, you need the total square footage, and then the coverage rate of the stain you are buying. Most deck stains cover 150 to 300 sq ft per gallon per coat, depending on the age, condition, and porosity of the wood. Enter your measurements in the deck stain estimator below for an instant answer.
- Most deck stains cover 150 to 300 sq ft per gallon on the first coat.
- Total square footage = floor (length x width) + railings (length x height) + steps (width x depth x number of steps).
- Weathered or porous wood uses 20 to 40 percent more stain.
- Second coats go up to 50 percent farther than the first.
- For fences, measure one side and double it if you’re staining both sides.
- Buy 10 to 15 percent extra.
- New wood under one year old gets one coat only. For transparent, semi-transparent, and semi-solid stains on wood less than one year old, apply only one coat. New wood is denser and less porous than weathered wood and will not absorb a second coat properly. See our full guide on staining new decks.
Contents
- Deck Stain Calculator
- Fence Stain Calculator and Estimator
- How to Calculate Deck Square Footage
- Coverage Rate by Stain Type
- How Much Prep Product Do You Need?
- Pro Tips on Buying the Right Amount
- Recommended Deck Stains
- Frequently Asked Questions
Deck Stain Calculator: Decking and Wood Stain Estimator
Use this decking stain calculator to estimate how many gallons you need for the floor, railings, and steps. It works as a wood stain calculator for any exterior wood project. Enter your measurements, then select your stain type and wood condition for the most accurate estimate.
Deck Stain Estimator
New wood less than one year old should receive only 1 coat of transparent, semi-transparent, or semi-solid stain. Learn more about staining new wood.
Fence Stain Calculator and Estimator
Use this fence stain estimator to calculate how many gallons you need for a fence. Enter the length of one side, and the estimator doubles it if you are staining both sides. Click the button to expand the calculator.
How to Calculate Deck Square Footage
How to calculate deck square footage by hand is simple once you break the deck into three parts: the floor, the railings, and the steps. These are the same formulas the deck stain estimator uses.
Wood Deck Stain Estimator Formula
Flooring Length x width =?
Railing Length x height =?
Steps Width x Depth x #of Steps =?
Add up all 3 for the Total Sq. footage.
Length x height =?
Multiply x 2 for both sides = Total Sq. Footage
Tips for Measuring Your Deck
When measuring your deck, use a tape measure or measuring wheel. Without a measuring tool, you can get a close approximation by pacing the deck off. A long stride is close to a yard, or 3 feet, so multiply the number of strides by 3 for the approximate length in feet. Do this for every section above to get the total square footage.
Be sure to add any less common areas: lattice, skirting, benches, pergolas, or other wood structures you plan to stain.
My Pro Advice: This calculator gives you an approximate estimate for most deck stain brands and types, and the actual amount varies by brand and type of stain. Always follow the label directions when applying. For more detail, see my guide on how much deck stain to buy. Once you know how much you need, you can order outdoor wood stain directly.
Coverage Rate by Stain Type
Coverage rates vary significantly by stain type and wood condition. Use this table as a starting point, then adjust based on the specific product label.
| Stain Type | Coverage Per Gallon* | Notes |
|---|---|---|
| Semi Transparent Oil Based | 150 to 250 sq ft | Penetrating; weathered wood absorbs more |
| Semi Transparent Water Based | 150 to 200 sq ft | Coverage is more consistent |
| Semi Solid Stain | 150 to 250 sq ft | Heavier pigment load; coverage varies by brand |
| Solid Color Stain | 150 to 300 sq ft | Two coats required; second coat covers more |
| * Coverage rates shown are per coat on the first application. Second coats typically cover up to 50% farther than the first coat, as the wood has already absorbed its initial saturation. | ||
My Pro Tip: New or smooth wood absorbs less stain than weathered, porous wood. If your deck boards are gray, rough, or deeply weathered, plan on using 20 to 40 percent more product than the label suggests. Always buy a little extra. You can return unopened cans or save them for the next maintenance cycle.
How Much Prep Product Do You Need?
Stain quantity is only half the equation, because you need to prep the wood before you stain. The coverage estimates below are based on Restore A Deck prep products, my recommended prep system.
| Prep Product | Typical Coverage | When You Need It |
|---|---|---|
| Deck Cleaner | 500 to 1,000 sq ft per kit | New or lightly weathered wood with no old stain |
| Deck Stain Stripper | 500 to 1,000 sq ft per kit | Any deck with old or failing stain that needs removal |
| Wood Brightener | 500 to 1,000 sq ft per kit | Always, after cleaning or stripping to neutralize pH |
Pro Tips on Buying the Right Amount
- Always buy extra. It is better to have a partial gallon left over than to run short mid project. You can return unopened cans to most retailers or save them for future maintenance coats.
- Factor in two coats on bare wood. Most penetrating stains on bare or stripped wood need two coats. The first coat absorbs deeply, and the second coat uses up to 50 percent less product because the wood is already partially saturated.
- Adjust for wood porosity. Older or heavily weathered wood can use 20 to 40 percent more stain than the label coverage rate suggests. New or smooth wood uses less.
- Fence coverage doubles. When calculating a fence, measure one side (length x height) and multiply by two for both sides.
- Do not forget railings and steps. Most homeowners underestimate how much stain goes on railings and stair stringers. Always add these to your total before buying.
Recommended Deck Stains
Now that you know how much stain you need, find the right product for your deck below.
Frequently Asked Questions About the Deck Stain Calculator
How many gallons of stain do I need for a 300 square foot deck?
For a 300 square foot deck floor with one coat of semi transparent stain at 150 to 250 square feet per gallon, you need 1 to 2 gallons. For two coats on bare or stripped wood, plan on 2 to 3 gallons total, since the second coat absorbs up to 50 percent less than the first. Add more if you are staining railings and steps, which can easily add another 100 to 150 square feet depending on the deck layout.
How much stain do I need for a fence?
Multiply the fence length by its height, then double it if you are staining both sides. A 100 foot fence that is 6 feet tall is 600 square feet per side, or 1,200 square feet for both sides. With two coats on rough sawn wood, that typically takes about 9 to 12 gallons. The fence stain estimator above adjusts for stain type and wood condition.
How do I measure my deck square footage for staining?
Measure the floor by multiplying length times width. Add railing square footage by multiplying the total linear length of all railings by their height, typically 3 feet. Add step square footage by multiplying the step width by the tread depth by the number of steps. Add all three for your full deck square footage. For a fence, multiply length by height, then multiply by two for both sides.
How much stain does a gallon cover on a deck?
Most deck stains cover 150 to 300 square feet per gallon on the first coat, depending on stain type and wood condition. Semi transparent oil based stains typically cover 150 to 250 square feet per gallon, and solid color stains cover 150 to 300. Weathered or porous wood absorbs more and pushes coverage toward the low end. Second coats go up to 50 percent farther than the first because the wood is already partially saturated.
Can I use this as a wood stain calculator for other projects?
Yes. The calculator works for any exterior wood you can measure in square feet, including siding, pergolas, benches, and skirting. Measure each area, add it to your deck or fence total, and use the same stain type and wood condition settings.
Do I need one coat or two coats of deck stain?
Most staining projects on bare or stripped wood need two coats for full protection and an even finish. The exception is new wood less than one year old. For transparent, semi transparent, and semi solid stains, apply only one coat, because the dense wood fibers will not absorb a second coat. See my guide on staining new decks for full details.
How much extra stain should I buy as a buffer?
I recommend buying at least 10 to 15 percent more than your calculated estimate. Porosity varies board to board, and rough or weathered sections often use more stain than expected. Unopened cans can be returned to most retailers. If you have leftover stain in an opened can, seal it tightly and store it in a climate controlled space. Most oil based stains stay usable for 1 to 2 years after opening.
Does the deck stain calculator account for railings and steps?
Yes. The calculator above has separate inputs for the deck floor, railings, and steps, so you get a full total rather than just the floor measurement. Forgetting railings and steps is one of the most common reasons people run short on stain mid project. If your deck has built in benches, lattice skirting, or a pergola, add those measurements to the total manually.
Have a question about how much stain you need? Ask in the comments below with your deck size and stain type, and I will help you figure it out.
