Deck Stain Calculator

Deck stain coverage depends on the wood type, condition, porosity, stain type (solid, semi-transparent, or clear), and application method. New rough-sawn wood absorbs much more stain than weathered smooth wood, so coverage rates vary significantly.

Coverage formula: Gallons Needed = Deck Area / Coverage Rate per Gallon

For two coats: Total Gallons = (Deck Area / Coverage Rate) × Number of Coats

What each variable means:

• Deck Area — total square footage of all horizontal and vertical surfaces to be stained: decking boards, railings (both sides), stairs (treads + risers), posts, and fascia boards
• Coverage Rate — stated on the product label; typical ranges:
  • Clear/water repellent: 200–400 ft²/gallon
  • Semi-transparent penetrating stain: 150–300 ft²/gallon
  • Solid color stain: 100–200 ft²/gallon (first coat); 200–300 ft²/gallon (second coat)
• Number of Coats — new/stripped bare wood typically needs 2 coats; maintenance coats on previously stained decks may need only 1 coat
• Waste Factor — add 10–15% for brush/roller waste, overspray, and uneven wood absorption; 20% for rough-sawn or cedar/redwood that is particularly thirsty

Worked example: Deck: 16’ × 24’ main platform = 384 ft² Railings: 80 linear feet × 3.5’ (both sides = 7’) = 560 ft² Stairs: 5 treads × 4’ wide = 20 ft² Total area = 384 + 560 + 20 = 964 ft² With 15% waste factor: 964 × 1.15 = 1,108 ft²

Using semi-transparent stain at 200 ft²/gallon, 2 coats: First coat: 1,108 / 200 = 5.54 gallons → 6 gallons Second coat (sealing, better coverage): 1,108 / 250 = 4.43 gallons → 5 gallons Total: 11 gallons (buy 12 to have a partial can for touch-ups)

At $40/gallon: Material cost = $480

Pro tip: Apply stain on a dry day when temperature is 50–90°F and no rain is forecast for 24–48 hours. Stain on a cool, cloudy day to prevent premature drying that causes lap marks.