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How Much Deck Stain Do You Need?

Enter your deck floor, railing length, and steps → get the exact gallons and 5-gallon pails of stain to buy for 1 or 2 coats, plus typical material cost.

Last updated: November 10, 2026

ft
ft
linear ft

Assumes 3 ft railing height (×3 sq ft per linear ft) — change in Advanced.

steps

Assumes 4 ft wide × 18 in tread+riser (6 sq ft/step) — change in Advanced.

Standard maintenance coat on weathered pressure-treated or cedar decking.

Smooth / new: tight grain, 250 sq ft/gal

Average: previously stained, 175 sq ft/gal

Rough / weathered: dry open grain, 125 sq ft/gal

Stain Order Summary

Deck Stain to Buy
4 gallons
Best mix: 4 × 1-gal cans
3.84 gal exact (1.92 gal/coat × 2) · 0.16 gal spare
5-Gallon Pail Tip: Buying 1 × 5-gal pail ($210–$270 each) usually costs about the same as 4 single-gallon cans ($180–$260) and leaves 1.16 gal sealed for future touch-ups.
Total stainable area:336 sq ft
• Deck floor:192 sq ft (57%)
• Railings (40 ft × 3 ft):120 sq ft (36%)
• Stairs (4 steps):24 sq ft (7%)
Coverage rate used:175 sq ft/gal per coat
Gallons per coat:1.92 gal × 2 coats
Spare after whole gallons:0.16 gal
Typical retail cost:≈ $180–$260

Based on $45–$65/gal · $210–$270/5-gal pail. Enter your local store prices in Advanced settings for an exact total.

Worked Examples

12 × 16 ft Deck + Railings + Stairs

40 ft railing · 4 steps · Average wood (175 sq ft/gal) · 2 coats

  • Stainable area: 336 sq ft (192 floor + 120 railing + 24 stairs)
  • Per coat: 1.92 gal
  • Exact needed: 3.84 gal
  • Order: 4 gallons (4 × 1-gal cans)
  • 0.16 gal spare — or buy 1 × 5-gal pail for roughly the same price

20 × 20 ft Deck: Floor vs Full Deck

Average wood (175 sq ft/gal) · 2 coats

  • Stainable area: 400 sq ft floor only vs 604 sq ft with 60 ft railing & 4 steps
  • Per coat: 2.29 gal (floor) vs 3.45 gal (full)
  • Exact needed: 4.57 gal (floor) vs 6.90 gal (full)
  • Order: 5 gal (1 pail) vs 7 gal (1 pail + 2 cans)
  • Railings and steps add 204 sq ft (+51% more stain)

10 × 12 ft Patio Deck Maintenance

32 ft railing · 3 steps · Smooth wood (250 sq ft/gal) · 1 coat

  • Stainable area: 234 sq ft (120 floor + 96 railing + 18 stairs)
  • Per coat: 0.94 gal
  • Exact needed: 0.94 gal
  • Order: 1 gallon (1 × 1-gal can)
  • 0.06 gal spare — single maintenance coat

Deck Stain Coverage by Wood Condition & Opacity

Outdoor decking absorbs far more finish than interior drywall. While wall paint covers 350–400 sq ft per gallon, deck stain averages 175 sq ft per gallon and drops to 125 sq ft per gallon on dry, weathered boards.

Wood ConditionPer 1-Gal Can (1 Coat)Per 5-Gal Pail (1 Coat)Typical Deck Surface
Smooth / New Wood250 sq ft1,250 sq ftPlaned new pressure-treated pine, cedar, or a 1-coat maintenance refresh
Average / Previously Stained175 sq ft875 sq ftStandard weathered residential decks cleaned and ready to restain
Rough / Weathered Bare Wood125 sq ft625 sq ftDry, cracked, gray timber or rough-sawn lumber that drinks up stain

Stain Opacity & Recoat Lifespan

Stain Type1st-Coat CoverageTypical CoatsRecoat CycleBest Use Case
Clear / Transparent Sealer200–300 sq ft/gal1 coatEvery 1–2 yearsShows full wood grain; lowest UV protection.
Semi-Transparent Stain150–225 sq ft/gal1–2 coats (wet-on-wet)Every 2–3 yearsMost popular choice; penetrates wood without peeling.
Semi-Solid Stain150–200 sq ft/gal1–2 coatsEvery 3–4 yearsHides mild blemishes while keeping wood texture visible.
Solid Color Acrylic Stain125–175 sq ft/gal2 coatsEvery 4–5 yearsOpaque film like paint; covers heavy weathering and color changes.

How We Calculate

Floor Area = Floor Length × Floor Width
Railing Area = Railing Linear Length × Railing Height (default 3 ft)
Stairs Area = Steps × Step Width (4 ft) × (Tread + Riser ÷ 12) (1.5 ft)
Total Area = (Floor + Railing + Stairs) × (1 + Buffer %)
Total Gallons = (Total Area ÷ Coverage Rate) × Coats

Note: A second coat on wood often spreads 25%–35% farther than the first coat. Sizing both coats at the first-coat coverage rate provides a built-in safety margin so you do not run out mid-board or mix dye lots.

Frequently Asked Questions

One gallon of deck stain covers 125 to 250 sq ft per coat, averaging about 175 sq ft per gallon on standard residential decking. Smooth or newly planed wood reaches around 250 sq ft per gallon, while dry, cracked, or heavily weathered wood absorbs more and drops to about 125 sq ft per gallon. A 5-gallon pail covers 625 to 1,250 sq ft per coat.
For a 20×20 ft deck floor alone (400 sq ft) at the standard 175 sq ft per gallon rate, you need 2.29 gallons for 1 coat (buy 3 gallons) or 4.57 gallons for 2 coats (buy one 5-gallon pail). If your 20×20 deck includes 60 linear feet of 3-foot railing (+180 sq ft) and 4 steps (+24 sq ft), the total stainable area rises to 604 sq ft, requiring 3.45 gallons for 1 coat (buy 4 gallons) or 6.90 gallons for 2 coats (buy one 5-gallon pail plus two 1-gallon cans).
At 175 sq ft per gallon, staining 1,000 sq ft of total deck surface takes 5.71 gallons for 1 coat (buy 6 gallons: one 5-gallon pail + one 1-gallon can, about $255–$335 in stain) or 11.43 gallons for 2 coats (buy 12 gallons: two 5-gallon pails + two 1-gallon cans, about $510–$670 in stain). Adding deck cleaner, brightener, pads, and brushes ($60–$120) puts total DIY cost at roughly $315–$790. Hiring a pro crew typically costs $1,500–$3,500 ($1.50–$3.50 per sq ft) including pressure washing and prep.
You do not need to measure individual spindles. Multiply the total linear length of your railing by its height (for example, 40 ft × 3 ft = 120 sq ft). Treating the railing like a solid wall accounts for coating all four sides of the balusters plus the top and bottom rails and posts. For stairs, multiply the number of steps by the step width and the combined tread-plus-riser depth (typically 4 ft wide × 1.5 ft per step = 6 sq ft per step).
Apply 1 coat for routine maintenance over an existing compatible stain in good condition, or on dense new lumber less than a year old. Apply 2 coats on bare, stripped, or weathered wood, or when using a solid-color stain. Note that with penetrating oil stains, the second coat is usually applied wet-on-wet within 20–30 minutes and uses 25%–35% less stain than the first coat; this calculator sizes both coats at the full rate so you do not run short mid-board.

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