Deck Stain Calculator

A deck stain calculator returns how many gallons of stain or sealer a deck needs. It multiplies the surface area by the number of coats, then divides by the product's coverage rate in square feet per gallon. The result rounds up to a whole gallon, since stain is bought by the container.

Last reviewed September 2026Method & sources Report an error

Stain Needed

4 gal

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Deck stain / sealer4 gallons

Breakdown
Stain Needed	4 gal
Total Coverage Needed (area × coats)	640 sq ft
Estimated Cost

How to Calculate Deck Stain

Multiplying the deck's surface area by the number of coats gives the total area of stain that needs to be applied. A 320 sq ft deck with 2 coats needs 640 sq ft worth of coverage, not 320. Dividing that by the product's coverage rate gives the raw gallons needed. The coverage rate is printed on the can, commonly 100-300 sq ft per gallon per coat. The result is rounded up to a whole gallon, since stain is bought by the container.

Example: 320 sq ft deck, 2 coats, at 200 sq ft/gal coverage

A 320 sq ft deck, 2 coats, at 200 sq ft/gal coverage: 1. Total coverage needed: 320 × 2 = 640 sq ft 2. Gallons needed: 640 ÷ 200 = 3.2, rounded up to 4 gallons Switching to a more porous, rough-sawn deck at 150 sq ft/gal coverage instead would raise that to 640 ÷ 150 = 4.27, rounded up to 5 gallons for the same deck and coat count.

Deck Stain: Compare Scenarios

Scenario	Stain Needed	Total Coverage Needed (area × coats)
Small (150 sq ft deck)	2 gal	300 sq ft
Medium (320 sq ft deck)	4 gal	640 sq ft
Large (800 sq ft deck)	8 gal	1,600 sq ft

What Is Deck Stain?

A deck stain calculator converts a deck's surface area, coat count, and a product's coverage rate into the number of gallons to buy. Coverage rate varies more for deck stain than interior paint, since it depends heavily on how porous and weathered the wood is. New, smooth wood soaks up less product per coat than rough-sawn or previously weathered wood, which is why this calculator keeps the coverage rate directly adjustable rather than fixing it to one number.

Deck Stain: Pros and Cons

Pros

Rounds up to a whole gallon automatically, so you don't have to do the ceiling-division by hand before heading to the store
Coverage rate is a direct, adjustable input rather than a fixed number, since it varies by product and by how porous or weathered the specific deck is
Separates total coverage (area × coats) from gallons needed, so you can see exactly why two coats on the same deck costs more than one

Cons

Doesn't measure deck area for you. A multi-level deck, a deck with built-in benches or planters, or one with a lot of railing needs its own area measurement or estimate before using this calculator
Doesn't distinguish between stain types (transparent, semi-transparent, solid). Each has a different typical coverage rate, so check your specific product's label and adjust the coverage input accordingly
Assumes uniform coverage across the whole deck. Heavily weathered or previously-stained sections may need a different rate than freshly sanded boards on the same deck

Deck Stain: What a Pro Checks

Check the coverage rate printed on your specific product's label rather than assuming a flat number. Deck stain runs 100-300 sq ft per gallon per coat, and rough-sawn or weathered wood soaks up noticeably more than new, smooth wood.
Include railings, balusters, and stairs in your area total if you're staining the whole structure in one job. It's easy to undercount how much surface area they add.
Two coats is standard for new or bare wood. A deck being refreshed rather than freshly built sometimes only needs one coat, so check your product's specific recommendation before buying for two.

Frequently Asked Questions

How much deck stain do I need per square foot?

It depends on the product and the wood's condition, but deck stain and sealer labels commonly list coverage of 100-300 sq ft per gallon per coat. New, smooth wood tends toward the higher end of that range. Rough-sawn or weathered wood soaks up more product and lands toward the lower end.

How many gallons of stain do I need for a 300 sq ft deck?

At a typical 200 sq ft/gal coverage rate with 2 coats, about 3 gallons (300 × 2 ÷ 200 = 3 exactly). A more porous or rough-sawn deck at 150 sq ft/gal would need 4 gallons for the same area and coat count.

How many coats of stain does a deck need?

Two coats is the most common recommendation for new or bare wood, giving fuller color and better protection than one coat. A single coat is sometimes used for a lighter, more natural look or on a deck being refreshed rather than freshly built. Check your specific product label for its recommendation.

Does deck stain cover more or less than paint?

Generally less, and more variably. Deck stain coverage (100-300 sq ft/gal) tends to run lower and wider-ranging than interior wall paint (typically 350-400 sq ft/gal). That is because stain is applied to a more porous, horizontal, weather-exposed surface that absorbs more product per coat.

Should I stain the railings and balusters too, or just the deck boards?

Most people stain the entire structure (deck boards, railings, balusters, and stairs) for a uniform look and consistent weather protection. Include their surface area in your total square footage input if you're staining them in the same job, since it's easy to undercount the added surface area of balusters and railings.

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