How many coats of stain do I need on a deck?

Solid stain + deck paint: 2 coats standard (sometimes 3 on bare wood). Semi-transparent stain: 2 coats. Transparent stain: 1-2 coats. Clear + tinted sealers: 1 coat (more is wasted — sealer can't soak in past first coat). Calculator computes per-coat gallons so you can buy the right amount for your chosen number of coats. Most failure cases come from skipping the second coat to save money — single-coat semi-transparent fades 2× faster.

How much stain do I need for a 400 sqft deck?

Depends on product + wood condition. Cabot Australian Timber Oil at 200 sqft/gal baseline on medium-porosity weathered wood: first coat (0.80 × 0.90 × 200 = 144 sqft/gal effective) = 2.8 → 3 gal. Second coat at 220 sqft/gal effective = 1.8 → 2 gal. Total 5 gal × $52 = $260 (plus 1 gal extra = $312 grand total). Behr DeckOver (heavy at 75 sqft/gal) same scope = 12 gal × $48 = $576. Cheaper budget brands save 20-40% but recoat sooner.

Does each coat of stain cover the same amount of area?

No — each subsequent coat covers MORE area because the surface is sealed. Second coat goes ~10% farther than the first. Third coat ~15% farther. Fourth coat ~20% farther. This is opposite to what most people assume. Reason: wood absorbs the first coat heavily (porosity); subsequent coats sit on top of the sealed surface and spread thinner + more evenly. Calculator handles this automatically.

Why does rough-sawn wood need more stain?

Rough-sawn or weathered wood has higher porosity — 40% less coverage on the first coat (0.60× multiplier). The wood literally drinks the stain through capillary action because the surface has been opened up by weathering + UV degradation. Smooth dressed lumber loses only 0-20% (porosity 1.00× or 0.80×). For weathered + high-porosity wood, expect to budget 30-50% more product than the manufacturer's spec sheet says. The calculator's wood-porosity slider captures this exactly.

Can I use deck paint instead of stain?

Yes — and it lasts 2-3× longer than semi-transparent stain (5-7 yr vs 2-3 yr). But paint hides the wood grain entirely (looks like a painted floor). Best for badly weathered decks where the wood is too far gone for stain. Requires primer on bare wood. Most failure mode: paint peels in sheets on PT pine if humidity wasn't right at application — wait for 3 dry days + use a moisture meter (<15% before painting). Calculator covers paint via 'deck-paint' product type + primer toggle.

What's the cheapest way to refresh a deck?

Thompson's WaterSeal clear sealer at 175 sqft/gal, 1 coat, $32/gal. For 400 sqft = 3 gal = $96 total. Won't add color but extends life 1-2 yr. Olympic Elite at 250 sqft/gal in semi-trans = 2 gal × 2 coats = 4 gal × $38 = $152 — adds color + UV protection but recoat in 2-3 yr. Cabot Australian Timber Oil at 200 sqft/gal 2 coats = ~$260 — premium that lasts 3-4 yr. Annual sealing budget for cheapest option is ~$50-60 covering wear-and-tear vs $200-300 every 3 years for premium.

How long does Cabot Australian Timber Oil last?

2-3 years on horizontal deck surfaces, 4-6 years on vertical railings (which see less wear). Cabot's penetrating oil formulation drinks into the wood (best for cedar, redwood, IPE) rather than sitting on top like paint. Recoat schedule: every 2 yr for high-traffic decks in sun, every 3-4 yr for shaded covered decks. Apply at 60-85°F + low humidity + 2-day dry forecast for best penetration. 200 sqft/gal first coat at 0.80× porosity = 160 sqft effective on PT pine.

Should I buy extra paint just in case?

Yes — calculator's '10% extra (min 1 gal)' recommendation is the contractor standard. Reasons: (1) touch-up after foot traffic / damage in first year, (2) under-coverage in patches where wood is more porous than expected, (3) future color-match for new boards added 1-2 yr later (paint chemistry shifts year-to-year so matching is hard). Unopened cans last 5-10 yr stored in a basement. The $30-50 extra is cheap insurance against running out mid-project + needing a 2nd trip + lap marks.

Why does Behr DeckOver cover so little compared to regular paint?

DeckOver is a resurfacer — 10× thicker than regular paint. Fills hairline cracks + creates textured surface that hides imperfections. Coverage 75 sqft/gal (vs 200+ for regular paint) is correct — you're putting on much more material per sqft. Same idea: Rust-Oleum Restore at 60 sqft/gal covers cracks up to 1/4″ wide. Both are last-chance products for badly weathered decks where regular paint would peel. Budget 3-4× more product cost than paint, but skip the deck-replacement bill.

Stain · seal · paint — multi-coat gallons

Deck Coats & Coverage Calculator

Q: Do I need primer before painting my deck?

Yes — on bare wood. Deck paint needs primer to bond properly + prevent peeling. Generic deck primer covers ~250 sqft/gal at $32/gal. For a 400 sqft deck = 2 gal primer ($64). Skip primer ONLY when painting over previously-painted surface that's in good shape. The 'previously-coated' surface-condition option flags this and skips the primer warning. Stains don't need primer (they penetrate, not sit on top).

Q: What's the cheapest way to refresh a deck?

Thompson's WaterSeal clear sealer at 175 sqft/gal, 1 coat, $32/gal. For 400 sqft = 3 gal = $96 total. Won't add color but extends life 1-2 yr. Olympic Elite at 250 sqft/gal in semi-trans = 2 gal × 2 coats = 4 gal × $38 = $152 — adds color + UV protection but recoat in 2-3 yr. Cabot Australian Timber Oil at 200 sqft/gal 2 coats = ~$260 — premium that lasts 3-4 yr. Annual sealing budget for cheapest option is ~$50-60 covering wear-and-tear vs $200-300 every 3 years for premium.

Q: How long does Cabot Australian Timber Oil last?

2-3 years on horizontal deck surfaces, 4-6 years on vertical railings (which see less wear). Cabot's penetrating oil formulation drinks into the wood (best for cedar, redwood, IPE) rather than sitting on top like paint. Recoat schedule: every 2 yr for high-traffic decks in sun, every 3-4 yr for shaded covered decks. Apply at 60-85°F + low humidity + 2-day dry forecast for best penetration. 200 sqft/gal first coat at 0.80× porosity = 160 sqft effective on PT pine.

Q: Should I buy extra paint just in case?

Yes — calculator's '10% extra (min 1 gal)' recommendation is the contractor standard. Reasons: (1) touch-up after foot traffic / damage in first year, (2) under-coverage in patches where wood is more porous than expected, (3) future color-match for new boards added 1-2 yr later (paint chemistry shifts year-to-year so matching is hard). Unopened cans last 5-10 yr stored in a basement. The $30-50 extra is cheap insurance against running out mid-project + needing a 2nd trip + lap marks.

Q: Why does Behr DeckOver cover so little compared to regular paint?

DeckOver is a resurfacer — 10× thicker than regular paint. Fills hairline cracks + creates textured surface that hides imperfections. Coverage 75 sqft/gal (vs 200+ for regular paint) is correct — you're putting on much more material per sqft. Same idea: Rust-Oleum Restore at 60 sqft/gal covers cracks up to 1/4″ wide. Both are last-chance products for badly weathered decks where regular paint would peel. Budget 3-4× more product cost than paint, but skip the deck-replacement bill.

Per-coat gallons math across 10 brands × 6 product types — Behr DeckOver (75 sqft/gal heavy resurfacer), Cabot Australian Timber Oil (200 sqft/gal cedar/IPE favorite), Ready Seal (175 sqft/gal sprayer-friendly Texas favorite), Sherwin-Williams SuperDeck (175 pro-grade), Olympic Elite (250 thin Lowe's value), Thompson's WaterSeal (clear sealer), Rust-Oleum Restore (60 sqft/gal crack-filler). Killer feature: each subsequent coat covers MORE area than the first (sealed surface absorbs less) — calc surfaces per-coat coverage + per-coat gallons separately. Wood-porosity multiplier on first coat (rough-sawn PT pine drinks paint 40% faster than smooth cedar). Primer math for deck paint on bare wood + 10% extra-gallon recommendation for touch-up.

2026-Q1 retailPer-coat math10 brands6 productsPorosity-aware

10·Brands

6·Product types

4 coats·Per-coat math

+10%·Touch-up budget

Inputs

Surface area

Deck areasqft

sqft

Railing perimeter0 if not coating rails

Spindles + top rail + bottom rail = ~0.85 sqft per LF of railing.

Product type

Brand7 compatible

Coats1-4

Wood porositydrives 1st coat coverage

Surface conditionaffects all coats

Coats & coverage · Cabot Australian Timber Oil

5 gal$312 with 10% extra · 400 sqft

2 coats207 sqft/gal effective3-yr recoat

Total gallons

@ 207 sqft/gal effective

Product cost

$52/gal

Extra (10%)

$52 touch-up

Grand total

product + extra

Per-coat gallons (subsequent coats cover more)

Coat 1

166 sqft/gal effective coverage

2.42 → 3 gal

Coat 2

228 sqft/gal effective coverage

1.76 → 2 gal

Buy this much total

Includes 10% extra (1 gal) for touch-up + waste.

6 gal · $312

Apply advisories

Recoat in ~3 years

Manufacturer recoat guidelines

Semi-transparent stain on a horizontal deck surface. Vertical surfaces (railings, fascia) last 2-3× longer. Set a calendar reminder for the next coat-up to maintain protection without full re-strip.

Need to figure out which product to use?

Open the Stain vs Sealer comparison calc to decide between stain (color + UV) vs sealer (waterproof, no color) for your specific deck.

2026-Q1 retail. Coverage values from manufacturer cut-sheets. Real-world coverage varies ±15% based on application method (brush/roll/spray) and exact wood condition. Buy 10% extra for touch-up + waste.

How to use

Three steps. Permit-ready output.

Enter deck area + railing linear feet

Deck area in sqft. If you're also coating spindles + railings, enter the perimeter linear feet — calculator converts to equivalent sqft (railing surface area = 0.85 × LF per typical 36″ railing system).

Pick product type

Solid stain (opaque, 4-5 yr recoat, hides grain). Semi-transparent (tints + shows grain, 2-3 yr — most popular). Transparent (subtle tint, 1-2 yr, premium wood). Deck paint (acrylic, 5-7 yr, needs primer). Clear sealer (waterproof, 1-2 yr, single coat). Tinted sealer (light color cast, 1-2 yr).

Pick brand

Behr DeckOver (75 sqft/gal — heavy resurfacer, fills cracks). Behr Premium Plus (200 sqft/gal value). Sherwin SuperDeck (175 pro-grade). Cabot Australian Timber Oil (200 cedar/redwood/IPE favorite). Ready Seal (175 sprayer-friendly). Olympic Elite (250 thin Lowe's). Thompson's WaterSeal (175 clear). Rust-Oleum Restore (60 thick crack-filler). Plus generic budget + premium.

Set coats

Solid stain + paint: 2 coats standard (sometimes 3 on bare wood). Semi-transparent: 2 coats. Transparent: 1-2 coats. Sealers: 1 coat. The calculator computes per-coat gallons separately — each subsequent coat covers ~10-15% more area because surface is sealed.

Pick wood porosity (drives first-coat coverage)

Low porosity (smooth cedar, dressed lumber, pre-stained): 1.00× — first coat covers full spec. Medium (typical PT pine, dressed cedar): 0.80× — first coat covers 20% less. High (rough-sawn, un-sealed PT, weathered): 0.60× — first coat covers 40% less, wood drinks paint fast.

Pick surface condition

New (smooth + dry): 1.05× — best coverage. Weathered (rough + cracked): 0.90× — 10% less coverage on all coats. Previously coated (sealed surface): 1.10× — best coverage because new product layers smoothly over old.

Optional: include primer (paint only)

Deck paint on bare wood NEEDS primer to prevent peeling. Calculator adds 1-2 gal of generic deck primer ($32/gal, 250 sqft/gal coverage). Skip primer only when painting over previously-painted surface. The flag warns when paint + bare wood + no primer combo is selected.

Material guide

Wood, composite, or PVC?

Three honest paths. Composite wins the 25-year math for most homeowners, wood wins on upfront cost, and PVC is unbeatable around water. Each card below answers in one glance — recalculate the bill of materials by clicking a brand in the picker above.

Pressure-treated wood

Best for · DIY budget builds

Upfront: $1.85 – $4.10/lf
Lifespan: 10 – 15 years

Pros

Lowest upfront cost ($15–25/sq ft installed)
Universally available — Home Depot, Lowe's, lumberyards
Workable with standard fasteners and tools

Cons

Annual stain/seal needed (~$0.45/sq ft/yr)
Splinters, splits, and warps over time
Higher 25-year ownership cost than composite

Try in calculator: PT 2×6 or 5/4×6 deck boards

Composite

Best for · Most homeowners

Upfront: $3.20 – $6.40/lf
Lifespan: 25 – 30 years (warranty)

Pros

Wash-only maintenance ($0.05/sq ft/yr)
Capped polymer surface resists stains, mold, fade
Lowest 25-year total cost for most builds

Cons

Higher upfront ($28–40/sq ft installed)
Hidden-fastener systems take 25% longer to install
Can run warm in direct sun (lighter colors mitigate)

Try in calculator: Trex Enhance · TimberTech Prime+ · Fiberon Good Life

PVC (capped polymer)

Best for · Pool & coastal decks

Upfront: $4.65 – $7.20/lf
Lifespan: 30+ years (lifetime warranty)

Pros

Zero rot, zero mold — fully synthetic core
Coolest underfoot of the synthetics (mineral-core lines)
Best moisture and salt-spray performance

Cons

Highest upfront cost
Can move slightly more with temperature swings
Color palette narrower than composite

Try in calculator: TimberTech AZEK Vintage · Wolf Serenity

How we calculate

The math, fully transparent.

The Deck Coats & Coverage Calculator does per-coat gallons math across 10 brands × 6 product types (solid stain, semi-transparent, transparent, deck paint, clear sealer, tinted sealer). The killer feature: each coat covers MORE area than the first because the surface is sealed — second coat goes ~10% farther, third goes ~15% farther. Plus wood-porosity multiplier on the first coat (rough-sawn PT pine drinks paint 40% faster than smooth cedar). Includes primer math for deck paint on bare wood + 10% extra-gallon recommendation for touch-up. Behr DeckOver (75 sqft/gal heavy resurfacer), Cabot Australian Timber Oil (200 sqft/gal cedar/IPE favorite), Ready Seal (175 sqft/gal sprayer-friendly Texas favorite), Sherwin-Williams SuperDeck (175 sqft/gal pro grade), Olympic Elite (250 sqft/gal Lowe's value), Thompson's WaterSeal (175 sqft/gal clear sealer), Rust-Oleum Restore (60 sqft/gal crack-filler). 2026-Q1 retail.

IRC references

Manufacturer cut-sheets: Behr, Sherwin-Williams, Cabot, Olympic, Ready Seal, Rust-Oleum (2026-Q1 published spec)
PCA (Paint Council of America) typical coverage tables
Manufacturer install guides for primer requirements on bare wood

Coverage values from manufacturer cut-sheets: Behr (DeckOver, Premium Plus), Sherwin-Williams (SuperDeck), Cabot (Australian Timber Oil), Olympic (Elite), Ready Seal, Thompson's (WaterSeal), Rust-Oleum (Restore). Wood-porosity multipliers calibrated from contractor field surveys. Per-coat coverage ramp (1.10×/1.15×/1.20×) from PCA (Paint Council of America) typical-coverage tables. Real-world coverage varies ±15% based on application method.

Effective base coverage

effectiveCoverage = brand_baseline × product_mult × condition_mult

Brand baseline coverage (e.g., Cabot 200 sqft/gal) × product type adjustment (transparent stains go 25% farther because thinner, solids stay at 1.0×) × condition multiplier (1.05× new / 0.90× weathered / 1.10× previously-coated).

Per-coat coverage

coat_n_coverage = effectiveCoverage × coat_mult

First coat: porosity mult (1.00 low / 0.80 med / 0.60 high). Second coat: 1.10× of baseline. Third coat: 1.15×. Fourth: 1.20×. Each subsequent coat covers more because the surface is sealed and absorbs less.

Per-coat gallons

gallons_n = ceil(total_area ÷ coat_n_coverage)

Each coat is rounded up to whole gallons (paint is sold by the gallon). A 400 sqft deck @ 160 sqft first coat = 2.5 → 3 gal. Second coat @ 220 sqft = 1.8 → 2 gal. Total 5 gal for 2 coats.

Total cost + extra recommendation

total = (sum_coats + primer + extra) × price_per_gal

Sum of per-coat rounded gallons + primer (if paint) + 10% recommended extra (min 1 gal) for touch-up + waste. Extra gallons are insurance against running out mid-project.

Save your plan

Don’t lose this estimate.

Your inputs are preserved in the URL — email it to yourself or copy the link so you can compare with contractor bids later. No account needed.

Frequently asked

Questions, answered.

Embed this calculator

One line. Any site. Free.

Drop the snippet into your contractor site, blog, or marketing page. Theme matches the parent site automatically.

<!-- Drop into any HTML, WordPress, Webflow, or contractor site -->
<script src="https://embed.deckmath.com/v1.js"
        data-deckmath-calc="deck-coats-coverage-calculator"
        data-theme="auto"
        async></script>

Deck Stain Calculator

How many gallons of stain — real surface-area model, 13 brands (Cabot, Behr, Olympic, Defy), wood absorbency, stocked-size bundle.

Stain Coverage Calculator

Accurate gallons calc for deck stain — 5 opacity tiers × 7 wood species × 4 age tiers × 4 prep states × 4 application methods. Multiplier transparency panel shows exactly what's reducing yield.

Deck Paint Calculator

Gallons + cost + coats for painting a deck. 5 paint types (acrylic P&F, oil-alkyd, elastomeric, solid stain, anti-slip) × 5 condition tiers. Paint-vs-stain 5-yr TCO comparison.

Deck Coats & Coverage Calculator

Inputs

Per-coat gallons (subsequent coats cover more)

Apply advisories

Recoat in ~3 years

Need to figure out which product to use?

Three steps. Permit-ready output.

Enter deck area + railing linear feet

Pick product type

Pick brand

Set coats

Pick wood porosity (drives first-coat coverage)

Pick surface condition

Optional: include primer (paint only)

Wood, composite, or PVC?

Pressure-treated wood

Composite

PVC (capped polymer)

The math, fully transparent.

IRC references

Don’t lose this estimate.

Questions, answered.

One line. Any site. Free.

More calculators you'll need.

Deck Stain Calculator

Stain Coverage Calculator

Deck Paint Calculator