DECK STAIN CALCULATOR
A gallon of semi-transparent deck stain covers roughly 150–300 sq ft per coat, depending on the product and the wood; rough or weathered boards take more. This calculator uses 225 sq ft per gallon for semi-transparent, so the default 20 × 14 ft deck with railings and five stairs (about 617 sq ft) needs about 3 gallons per coat, 6 for two. Enter your own deck below for your number.
Pre-filled with a typical 20 x 14 ft deck with railings and 5 stairs. Adjust dimensions below.
DECK FLOOR DIMENSIONS
Floor area:
280 sq ft
RAILINGS
STAIRS
STAIN TYPE
COATS & PRICING
YOUR ESTIMATE
6
gallons of semi-transparent stain
$240
estimated stain cost @ $40/gal
$0.39
per sq ft
AREA BREAKDOWN
Rounded up from 5.5 to 6 gallons. Always buy whole gallons.
How Much Deck Stain Do I Need?
Most deck stains cover 150 to 300 sq ft per gallon on a single coat, depending on the stain opacity and wood condition. The default deck (280 sq ft of floor plus railings and stairs, about 617 sq ft) needs 6 gallons for two coats at 225 sq ft per gallon. Older, porous wood absorbs more product, while a previously stained surface needs less.
One can for comparison: OLYMPIC Quick Cover Semi-Transparent lists approximately 250 to 350 sq ft per gallon, depending on wood texture and porosity, and a single coat for semi-transparent hiding (two for solid hiding) (product page, read November 2026). Your can's label overrides any average.
Typical Coverage
150 - 300 sq ft / gal
Recommended Coats
1–2 coats (per the can)
Avg. Gallon Cost
$30 - $90
How to Calculate Deck Stain Coverage
- Measure the deck floor. Multiply length by width. A 20 x 14 ft deck = 280 sq ft of floor surface.
- Add railings. Multiply total linear feet of railing by railing height, then double it (both sides). Add 50% if your railing has balusters or spindles.
- Add stairs. Each step has a tread (top) and a riser (front face, typically 7.5 inches). Multiply step count by the combined tread + riser area.
- Choose stain type. Transparent stains cover the most area per gallon (200-350 sq ft), while solid stains cover the least (75-150 sq ft) because they deposit a thicker film.
- Multiply by coats. Follow the can. Some semi-transparent stains are a single coat (Olympic Quick Cover lists one coat for semi-transparent hiding), while solid coverage usually takes two. Multiply your area by the coats, divide by the coverage rate, and round up.
Coverage by Stain Type
| Stain Type | Coverage (sq ft/gal) | Best For |
|---|---|---|
| Transparent | 200 - 350 | New wood, cedar, showing natural grain |
| Semi-Transparent | 150 - 300 | Most decks, balanced color and grain |
| Semi-Solid | 100 - 200 | Weathered decks, hides imperfections |
| Solid | 75 - 150 | Older wood, maximum UV protection |
Coverage varies by wood species. Softwoods like pine and cedar absorb more stain than hardwoods like ipe or composite decking. Always check the manufacturer's label for product-specific rates.
Pro Tips for Deck Staining
Prep is everything
Power-wash or sand the deck before staining. Bare, clean wood absorbs stain evenly. Skip this step and you'll waste product on flaking old finish. Check our guide on fixing peeling finishes for prep techniques.
Watch the weather
Stain between 50-90 °F with no rain forecast for 24-48 hours. Direct sunlight causes stain to dry too fast, leaving lap marks. For cold-weather advice, see painting in cold weather.
Apply with the right tool
Use a stain pad, roller, or pump sprayer with back-brushing. Brushes push stain into the grain but take longer. If you own a paint sprayer, spraying then back-brushing is the fastest method for large decks.
Buy 10% extra
Wood porosity varies across the deck. End-grain on cut boards and joints absorbs 2-3x more stain. An extra 10% prevents a mid-project run to the store with a mismatched batch.
Need to estimate the full project cost including labor? Use our painting cost calculator or build a client-ready quote with the painting estimate template. For pricing guidance, see how to price painting jobs.
Deck Stain Questions
How much stain do I need for a 12 × 12 deck?
The floor is 144 sq ft. At this calculator's 225 sq ft per gallon for semi-transparent stain, that is about 0.64 gallon a coat: 1 gallon for one coat, 2 for two. Railings and stairs add more, and a can that lists a higher spread rate needs less.
How many coats of deck stain?
The can decides. Some semi-transparent stains are a single coat, while solid stains usually take two.
Does rough wood need more stain?
Yes. Rough, weathered or porous boards soak up more stain per square foot, so plan on the low end of the can's coverage range.