Deck Stain Calculator — How Much Stain Do I Need?
Enter your deck size, number of coats and stain type to get the gallons you need for the floor, plus an optional allowance for railings and stairs. No sign-up, no data stored.
Stain needed
How deck stain quantity is estimated
- Deck area (sq ft) = length x width of the decking surface.
- Allowance = +15% when railings, balusters or stairs are included.
- Adjusted area = deck area x (1 + allowance).
- Gallons = adjusted area x coats / coverage per gallon.
Stain is sold in gallons and quarts, and a gallon typically covers 250-300 sq ft of smooth decking with one coat. Rough-sawn or very weathered lumber drinks stain fast - budget 200 sq ft per gallon or a second coat.
Deck size → stain needed reference
Semi-transparent stain at 250 sq ft/gal, smooth decking, with 15% railing allowance.
| Deck size | Area | 1 coat | 2 coats |
|---|---|---|---|
| 10x10 | 100 sq ft | 1 gal | 1 gal |
| 10x12 | 120 sq ft | 1 gal | 2 gal |
| 12x14 | 168 sq ft | 1 gal | 2 gal |
| 12x20 | 240 sq ft | 2 gal | 3 gal |
| 16x24 | 384 sq ft | 2 gal | 4 gal |
Last updated: October 2026 · Estimates assume semi-transparent oil or water-based stain. Solid stain covers more; rough-sawn lumber covers less.
Deck stain FAQ
No - stain soaks into wood instead of forming a film, so a separate primer is pointless. What matters is clean, dry, weathered wood. If the deck was painted or sealed, strip or sand it back to bare wood first.
Solid-body stains last 2-4 years, semi-transparent 2-3 years, and transparent stains 1-2 years. South- and west-facing decks with full sun fade fastest. Re-coat when water stops beading on the surface.
A typical deck stain covers 250-300 sq ft per gallon with one coat on smooth decking. Rough-sawn lumber absorbs far more - plan on 150-200 sq ft per gallon and often a second coat.
Yes - balusters and stair risers add roughly 15% more surface than the floor alone. Our calculator includes an allowance toggle so you do not under-buy for a deck with full railings.
Yes, if the old coat is sound and dry and you use the same stain type (oil over oil, water over water). Semi-transparent over a darker old stain will darken the result; solid stain covers almost anything.
Related calculators & guides
How Much Deck Stain Do I Need?
Coverage math, prep steps and the difference between transparent, semi-transparent and solid stain.
Read the guide →