Deck Stain Calculator
Stain coverage varies with the wood's roughness and how many coats you apply. Enter your deck size and finish details to get a gallon count you can take to the store.
Result
- Deck area192sq ft
- Total coated area192sq ft
- Stain needed3gallons
- Exact before rounding2.56gallons
- Metric9.7litres
How it works
stain = (area ÷ coverage per gallon) × coats, rounded up to the nearest half gallon
- Deck area = 16 × 12 = 192 sq ft
- Top face only = 192 sq ft
- 2 coats at 150 sq ft/gal = 2.56 gallons
- Round up to nearest half gallon = 3 gal
How the deck stain calculator works
Stain manufacturers list coverage per gallon per coat. Rough, pressure-treated wood soaks up more and lands near 150 sq ft per gallon; smooth, sanded boards hold closer to 200.
Most decks get two coats: the first seals, the second evens out the color. Multiply area by coats before dividing by coverage.
Buying is rounded up to the nearest half gallon because partial gallons don't exist. Buy everything from one batch — dye lots differ between cans.
Formula
gallons = (area ÷ coverage per gallon) × coats, rounded up to ½ gal
Worked example: 12 × 16 ft deck, two coats
- Deck area = 12 × 16 = 192 sq ft
- Smooth sanded surface: 200 sq ft per gallon
- Two coats = 192 ÷ 200 × 2 = 1.92 gallons
- Round up to the nearest half gallon = 2 gallons
- If staining top and underside (railings): 192 × 2 ÷ 200 × 2 = 3.84 → 4 gallons
Stain coverage by surface
| Surface | Coverage per gallon | 100 sq ft needs | 200 sq ft needs |
|---|---|---|---|
| Rough / pressure-treated | 150 sq ft | 0.67 gal (1 with 2 coats) | 1.33 gal (1.5 with 2 coats) |
| Smooth / sanded | 200 sq ft | 0.5 gal (1 with 2 coats) | 1 gal (1.5 with 2 coats) |
Coverage per coat. Rough sawn wood drinks more stain than smooth, sanded wood.
Frequently asked questions
How much stain do I need for a 12×16 deck?
192 sq ft. On smooth wood at 200 sq ft per gallon, two coats need 1.92 gallons → buy 2 gallons. On rough pressure-treated wood at 150 sq ft per gallon, two coats need 2.56 → buy 3 gallons.
Do I need to stain the underside of deck boards?
For loose boards or railings being stained before install, yes — coat both faces to seal the wood evenly. For an already-built deck, most people stain only the top surface, which halves the area.
How long does deck stain last?
Transparent and semi-transparent stains on horizontal surfaces typically last 1–3 years before a maintenance coat. Solid stains last longer but hide the grain. Climate, sun exposure and foot traffic drive the variation.
What's the difference between stain and paint for a deck?
Stain penetrates the wood and wears gradually; paint sits on top and can peel. For horizontal deck surfaces, stain is easier to maintain because there's no peeling edge to scrape.