Deck Stain Calculator

Staining a deck takes more product than most people expect, and buying too little mid-project is a frustrating delay. Enter your deck length and deck width, select your stain coverage type (solid, semi-transparent, or clear), and optionally add your railing and steps dimensions to get the total gallons of stain needed. Secondary outputs break down your total area into deck surface, railing, and steps so you know exactly where the product is going.

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Coverage varies by stain opacity

Results

Stain Needed

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Total Area

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Deck Surface Area

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Railing Area

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Steps Area

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Frequently Asked Questions

How much deck stain do I need for a 20x20 deck?

For a 400 sq ft deck with semi-transparent stain (175 sq ft coverage per gallon), you would need approximately 2.3 gallons. It's recommended to round up to 3 gallons to ensure complete coverage.

How much will a gallon of deck stain cover?

Coverage depends on stain type: solid stains cover about 150 sq ft per gallon, semi-transparent stains cover 175 sq ft per gallon, and clear stains cover up to 225 sq ft per gallon.

Should I include railings in my stain calculation?

Yes, railings add significant surface area to your project. Measure the total linear feet of railing and multiply by the height to get the square footage that needs staining.

Do I need to account for steps when calculating stain needs?

Absolutely. Steps have both treads and risers that need staining. Each step adds the width times the depth plus the width times the rise height to your total area.

Why do coverage rates vary between stain types?

Solid stains are thicker and provide less coverage per gallon than transparent stains. The opacity and thickness of the stain directly affects how much surface area one gallon can cover.

Should I buy extra stain beyond the calculated amount?

Yes, it's recommended to purchase 10-15% extra stain to account for wood porosity, application method variations, and future touch-ups. Wood age and condition also affect absorption rates.

How do I measure my deck for stain calculation?

Measure the length and width of the main deck surface. For railings, measure the total linear feet and height. For steps, count the number of steps and measure width and depth of each tread.

Can I use this calculator for fence staining too?

While this calculator is optimized for decks, you can use it for fences by treating the fence panels as deck area and measuring the total length times height of the fence sections.