Deck Stain Calculator
Gallons of stain or sealer for a deck, by coats and coverage.
Input sheet
DIY at your own risk. Calcora's calculators and guides are general estimates and information only — not professional, engineering, legal, or safety advice. Always verify local building codes and permit requirements, and hire a licensed pro for electrical, gas, plumbing, structural, or any work you're not fully comfortable doing yourself.
Stain coverage is the number that decides between one can and three: smooth new decking might take a gallon 300 sq ft, while weathered grain drinks it at 150. This calculator multiplies deck area by coats and divides by real coverage.
How it works
Deck area × coats ÷ coverage per gallon, rounded up. Semi-transparent stain covers ~250 sq ft per gallon on smooth wood; rough or thirsty boards drink more.
The base area is the deck's footprint — length × width of the boards you will walk on. Coats multiply it: two coats of semi-transparent stain is the standard schedule, and the second coat usually spreads a bit further than the first on sealed grain.
Railings, balusters, stairs, and fascia are the hidden area. A railing run adds roughly 1.5 sq ft of stainable surface per linear foot once you count both sides and the balusters — a wrap-around railing can add a third to the job.
Gallons = deck area × coats ÷ coverage (sq ft per gallon), rounded up.
Worked examples
A 16 × 12 ft deck, two coats at 250 sq ft/gal. → 2 gallons.
192 sq ft × 2 = 384 sq ft to cover; ÷ 250 = 1.54, rounded up to 2 gallons.
A 20 × 16 ft deck, two coats, same coverage. → 3 gallons.
320 × 2 = 640; ÷ 250 = 2.56 → 3 gallons. Add railings and it becomes 4.
Tips & gotchas
- Clean and brighten the deck first — stain over gray, dirty wood fails in a year regardless of quantity.
- Check the can's own coverage number and plug it in; penetrating oils, semi-transparents, and solid stains differ widely.
- Stain when the wood is dry (a water drop should soak in, not bead) and out of direct midday sun so it penetrates before flashing off.
FAQ
One coat or two?
Two thin coats outlast one heavy coat. Solid stains almost always need two; some penetrating oils spec a single coat — check the can.
How often does a deck need re-staining?
Semi-transparent stains last 2–3 years on horizontal surfaces; solid stains 3–5. Verticals like railings go roughly twice as long between coats.
Stain or seal — what's the difference?
Clear sealers repel water but let UV gray the wood. Stains add pigment that blocks UV — the more pigment (semi-transparent → solid), the longer the protection.
Related calculators
Concrete Calculator · Paint Calculator · Flooring Calculator · Mulch Calculator · Gravel & Driveway Calculator