Deck Stain Calculator: How Much Stain Do I Need
Work out how many gallons of stain or sealer a deck project needs before you shop. Enter the deck length and width, the number of coats, the coverage printed on your can, and any linear feet of railing. The tool adds the floor area to the railing surface, multiplies by the coats, then rounds up to whole gallons because stain is sold by the can.
How to estimate deck stain
- Enter the Deck length and Deck width in feet.
- Set the number of Coats, usually one or two.
- Enter the Railing length in linear feet, or leave it at zero.
- Adjust Coverage per gallon if your can lists something other than 200 sq ft.
- Read the Deck area, Total to cover, and Stain to buy, then copy the estimate.
Examples
Mid-size deck with railing
12 by 16 ft deck, 2 coats, 40 ft railing, 200 sq ft per gallon
Deck area 192 sq ft, 624 sq ft to cover, buy 4 gallons
Small deck, no railing
10 by 10 ft deck, 2 coats, 0 ft railing, 200 sq ft per gallon
Deck area 100 sq ft, 200 sq ft to cover, buy 1 gallon
Large deck with a long railing run
14 by 20 ft deck, 2 coats, 60 ft railing, 200 sq ft per gallon
Deck area 280 sq ft, 920 sq ft to cover, buy 5 gallons
Frequently asked questions
How much stain do I need for a deck?
Multiply the deck length by the width for the floor area, add about 3 square feet per linear foot of railing, multiply the sum by the number of coats, then divide by the coverage on the can and round up. A gallon typically covers around 200 square feet per coat.
How much area does a gallon of deck stain cover?
Roughly 150 to 350 square feet per coat, depending on the product and how thirsty the wood is. New, rough, or weathered boards soak up far more than smooth, previously sealed decking. The calculator assumes 200 square feet per gallon, and you can change that field to match your can.
How many coats does a deck need?
Most film-forming and semi-transparent deck stains call for two coats for an even, durable finish. Some penetrating oils go on as a single heavy coat wiped back to the wood. Always follow the label, which is why the coats field is adjustable here.
Why is the railing counted separately?
A railing has a top rail, two vertical faces, and a run of balusters, so it adds a surprising amount of surface for its footprint. Estimating about 3 square feet of finished surface per linear foot captures the top, sides, and spindles without measuring each piece.
Does the estimate include stairs or fascia?
No. The tool covers the deck floor plus railing only. For stairs, skirting, or fascia boards, measure their surface area separately and either add it to the deck dimensions or buy a little extra stain to cover it.
Should I buy a little more than the estimate?
Yes. Buying slightly over lets you keep a wet edge, hit thirsty end grain and knots, and set aside matching stain for touch ups later. Because stain sells in whole gallons, the result already rounds up, but rounding a borderline job up one more can is smart insurance.
Can I use this for a sealer or a solid stain?
Yes. The math is the same for clear sealers, semi-transparent stains, and solid-color stains. Just enter the coverage rate for that specific product, since solid stains and thick sealers often cover less area per gallon than a thin penetrating oil.
What if my deck is not a plain rectangle?
Break an L-shaped or multi-level deck into rectangles, run each one through the tool, and add the gallons together. For a rough allowance on an irregular shape, use the length and width of the smallest rectangle that would contain it.
Is my project data stored anywhere?
No. Every figure is calculated in your browser as you type, and nothing about your deck dimensions is uploaded or saved on a server.
Learn more
- How to estimate and apply deck stain
Measuring a deck for stain, why coverage rates vary so much, how many coats to plan, and the prep that makes the finish last.
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