Deck & Fence Stain Calculator
How much deck or fence stain do you need? Gallons or liters by stain type, wood porosity and number of coats, rounded to real can sizes.
Your estimate
1.21 gal
Stain needed (incl. 10% waste)
- Suggested purchase
- 1 gal + 1 qt
- Area to stain
- 192 sq ft
- First-coat coverage
- 300 sq ft/gal (smooth / new or recently prepped)
- Later coats
- 420 sq ft/gal
- In liters
- 4.6 L
Show the math
- Deck = length × width = 192 sq ft
- No extra area
- Coverage: 300 sq ft/gal × 1 for smooth / new or recently prepped = 300 sq ft/gal first coat; 420 sq ft/gal after that
- Stain = area ÷ first-coat coverage + 1 × area ÷ later-coat coverage × (1 + 10%) = 1.21 gal
- Rounded to real container sizes: 1 gal + 1 qt
Shopping list & cost
| Item | Spec | Qty | Cost |
|---|---|---|---|
| Wood stain | Semi-transparent, 2 coats | 1 gal + 1 qt | — |
| Wood cleaner / brightener | prep before staining; check label coverage | 1 container | — |
| Stain pad / brush / pump sprayer | back-brush if spraying | 1 set | — |
Prices are what you enter under Advanced options. Estimates only — check stock and pricing with your supplier.
Quick answer A 16 × 12 ft deck (192 sq ft) in semi-transparent stain, two coats on smooth wood, needs about 1.21 gal including 10% waste — buy 1 gal + 1 qt. Weathered or rough-sawn wood can need 40–100% more. A 5 × 3.6 m deck needs 4.6 L (1 × 5 L). First coats typically cover 250–350 sq ft per gallon on smooth wood; later coats go further.
Method & assumptions
Area = Length × Width (deck) or Length × Height × Sides (fence) + extras First-coat coverage = Label coverage × porosity factor (1.0 / 0.7 / 0.5) Later coats = First-coat coverage × 1.4 Stain = (Area ÷ first + (coats − 1) × Area ÷ later) × (1 + waste %)
- Porosity factor
- smooth/new 1.0, weathered 0.7, rough-sawn 0.5
- Label coverage
- the "smooth surface" figure on the can; typical 250–350 sq ft/gal
- 1.4×
- later coats need less — TWP lists 150–200 then 200–300 sq ft/gal
Assumptions & limits
- Default first-coat coverage on smooth wood: transparent 250, semi-transparent 300, solid 350 sq ft per gallon — conservative ends of current label ranges (Cabot semi 450–650 smooth, 200–300 rough; SuperDeck semi-solid 350 smooth, 100–200 rough).
- Fences are treated as solid surfaces; picket and shadow-box fences have more edges to coat, which the waste factor covers.
- US purchase: 5 gal pails, then gallons and quarts. UK/AU: 5 L, 2.5 L and 1 L tins.
- New pressure-treated lumber usually needs to dry before staining — check with a water-drop test.
Rounding: purchase quantities are always rounded up to whole units as sold. See our methodology.
Diagram
How to use this calculator
- Choose the project: a deck floor (length × width), a fence (length × height × sides) or an area you already know.
- Add railings, stairs and benches as extra area — railings are roughly 3 sq ft per linear foot counting both sides.
- Pick the stain type and be honest about the wood: weathered gray boards and rough-sawn cedar soak up far more stain.
- Set the coats from the label — some oil stains are one coat (or two wet-on-wet); solid stains are two.
- If you know the can's smooth-surface coverage, enter it under Advanced options.
Worked examples
Imperial: 150 ft privacy fence, 6 ft high, both sides, rough-sawn cedar, 1 coat semi-transparent
- Area = 150 × 6 × 2 = 1,800 sq ft
- Coverage = 300 × 0.5 = 150 sq ft/gal → 12 gal; +10% = 13.2 gal
- Buy 2 × 5 gal + 3 gal + 1 qt
Metric: 4 × 3 m weathered deck + 3 m² railings, 2 coats semi-transparent
- Area = 15 m²; first coat 7.4 × 0.7 = 5.2 m²/L; second 7.2 m²/L
- 15 ÷ 5.2 + 15 ÷ 7.2 = 4.97 L; +10% = 5.5 L → 5 L + 1 L
In depth: deck & fence stain planning notes
Why wood condition changes the answer so much
Paint sits on top of a surface; penetrating stains soak into it. That makes coverage depend on the wood far more than with paint. Look at any stain can and you will see two figures: Cabot's semi-transparent deck and siding stain, for example, lists about 450–650 sq ft per gallon on smooth surfaces and 200–300 on rough ones. Weathered, gray, sun-dried boards are just as thirsty as rough-sawn lumber. The calculator starts from a conservative smooth-wood figure for your stain type and applies a porosity factor — 1.0 for smooth, 0.7 for weathered, 0.5 for rough-sawn — rather than one number that is wrong for most decks.
Later coats use less because the wood is already partly filled. TWP, for instance, lists 150–200 sq ft per gallon for the first coat and 200–300 for the second, so this calculator assumes later coats cover about 1.4 times as much. Do follow the label on how many coats to apply: many oil-based semi-transparent stains are designed as one coat, or two applied wet-on-wet, and a second coat on top of a dried first coat can stay tacky. Water-based and solid stains usually specify two coats.
Measuring decks and fences
For a deck, the walking surface is length × width, but railings, stairs, benches and the fascia add a lot. A railing has two faces plus balusters; counting about 3 sq ft per linear foot covers a typical 36 in baluster railing on both sides. Stairs are roughly the tread and riser area of every step plus the stringers. For a fence, multiply length × height × the number of sides you will stain; picket and shadow-box fences have more edges than a solid board fence, and the 10% waste allowance plus a weathered or rough setting usually covers them.
Preparation decides how good the result looks and how long it lasts. Clean the wood with a deck cleaner, use a brightener after strippers, and let it dry — usually 48 hours — before staining. New pressure-treated lumber often needs weeks to dry out; sprinkle water on it, and if it beads, wait. Stain two or three boards at a time end to end to avoid lap marks, back-brush after spraying, and mix all the cans together before you start so the color is even across the whole job.
Reference table
| Stain | Smooth · weathered · rough-sawn |
|---|---|
| Transparent / toner | 250 · 175 · 125 |
| Semi-transparent | 300 · 210 · 150 |
| Solid color | 350 · 245 · 175 |
| Second coat (any) | ≈ 1.4 × first coat |
| Metric (semi, m²/L) | 7.4 · 5.2 · 3.7 |
Key facts
- Semi-transparent
- shows grain; 1–2 coats; re-coat every 2–3 years
- Solid stain
- film-forming; 2 coats; best on rails and siding
- Weathered wood
- clean and brighten first; drinks ~40% more
- Weather
- most stains need 24–48 h dry, above ~50 °F
Tips & common mistakes
- Clean and brighten the wood first — stain on gray, dirty wood looks blotchy and wears quickly.
- Stain two or three boards at a time along their full length to avoid lap marks.
- Back-brush or back-roll after spraying so the stain works into the grain.
- Buy all the stain at once and box (mix together) the cans so the color is consistent.
Frequently asked questions
How much deck stain do I need for a 12 × 12 deck?
144 sq ft: about 0.5 gal for one coat of semi-transparent on smooth wood, or 0.9 gal for two coats with 10% waste — buy 1 gallon. Weathered wood needs about 1.3 gallons.
How many square feet does a gallon of stain cover?
On smooth wood about 250–350 sq ft per gallon for a first coat, and up to 400–600 for some semi-transparents. On rough or weathered wood, 100–300. Check the can.
How much stain do I need for a fence?
Multiply length × height × sides. A 100 ft, 6 ft fence stained on both sides is 1,200 sq ft — about 4.4 gal for one coat of semi-transparent on smooth boards, or 8.8 gal on rough-sawn cedar.
Do I need one or two coats of deck stain?
Follow the label: many oil-based semi-transparents are a single coat (or two wet-on-wet on thirsty wood); water-based and solid stains usually need two.
Does the second coat of stain use less?
Yes, because the wood is partly sealed. TWP, for example, lists 150–200 sq ft/gal for the first coat and 200–300 for the second; this calculator assumes 1.4× the first-coat coverage.
Sources
- Behr – Premium Semi-Transparent Waterproofing Stain & Sealer — accessed : “Spread Rate: 1st Coat 250-300 Sq. Ft 2nd Coat 500-600 Sq. Ft. · 2 Thin Coats Required”
- Cabot – Semi-Transparent Deck & Siding Stain technical data (coverage) — general reference — not cited for a specific figure
- TWP Stain – what is the coverage rate for TWP? — general reference — not cited for a specific figure
- USDA Forest Products Laboratory – Wood Handbook, finishing of wood — general reference — not cited for a specific figure
Default values (yields, coverage rates and densities) are typical figures from manufacturer literature. Always check the label on the product you buy.
Related calculators
- Deck Board CalculatorWork out how many deck boards, joists, screws or hidden clips you need for a deck, using real board widths, gaps and stock lengths.
- Fence CalculatorEstimate fence posts, rails, pickets or panels and post-hole concrete for any fence length, with gates and real post sizes.
- Paint CalculatorWork out gallons or liters for a room, including textured walls at 200–300 sq ft per gallon, plus doors, coats and tin sizes.
Learn more in our guides
Method, waste and worked examples: Paint coverage: coats, waste and tin sizes.
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DIYCalcLab. “Deck & Fence Stain Calculator.” Oct 19, 2026. https://diycalclab.com/paint/stain-calculator/
Estimates only. Verify quantities with your supplier and local building codes. For structural, electrical or safety-critical work, consult a licensed professional. Full disclaimer.