Deck Stain Calculator
How much stain for a deck or fence
Staining a deck or fence? Enter the surface area to estimate the gallons of stain you'll need.
How much deck stain does a gallon of stain cover?
Stain coverage is the number everything else depends on. The same figures apply if you are using this as a wood stain calculator or a deck paint calculator, though solid products sit higher on the surface.
The calculator uses 250 ft² per gallon per coat, a reasonable middle figure. Real coverage swings enormously with how thirsty the wood is, and this is the single biggest source of under-buying:
| Surface | Coverage | Notes |
|---|---|---|
| Smooth, new, planed wood | 300 to 400 ft² | Least absorbent |
| Semi-transparent on smooth wood | 250 to 350 ft² | The common case |
| Solid stain | 200 to 300 ft² | Sits more on the surface |
| Weathered or rough sawn | 150 to 250 ft² | Drinks it; budget generously |
| Rough sawn fence boards | 150 to 250 ft² | Often needs double the smooth figure |
Rough or weathered wood can take twice what smooth new lumber does. If your deck has been down a few seasons and never sealed, plan against the low end of that range rather than the number on the can, which is always quoted for ideal conditions.
Deck stain by deck size
| Deck | Area | One coat | Two coats |
|---|---|---|---|
| 10 × 12 ft | 120 ft² | 0.5 gal | 1.0 gal |
| 12 × 16 ft | 192 ft² | 0.8 gal | 1.6 gal |
| 16 × 20 ft | 320 ft² | 1.3 gal | 2.6 gal |
| 20 × 24 ft | 480 ft² | 1.9 gal | 3.8 gal |
Add roughly 20% for railings, balusters and stairs, and more if the balusters are turned or ornate — a spindled railing has a startling amount of surface area for its apparent size. The easiest approach is to add that percentage to the deck area you enter above rather than trying to measure each part.
Using it as a fence stain calculator
Fences catch people out because they have two sides and most people budget for one. A 100 ft fence at 6 ft tall is 600 ft² per face, so 1,200 ft² in total before you count posts and rails.
| Surface | Coverage | Gallons per coat |
|---|---|---|
| Smooth or previously sealed | 250 ft²/gal | 4.8 gal |
| Rough sawn timber | 175 ft²/gal | 6.9 gal |
To use this as a fence stain calculator square feet tool, enter the fence length and double the height — a 100 ft by 6 ft fence becomes 100 × 12 — so both faces are covered in one figure. The fence calculator works out the posts and panels themselves.
Transparent, semi-transparent or solid
| Type | Shows grain | Lasts | Recoating |
|---|---|---|---|
| Clear sealer | Fully | 1 year | Easy, just reapply |
| Transparent | Almost fully | 1 to 2 years | Easy |
| Semi-transparent | Mostly | 2 to 3 years | Easy, the usual choice |
| Semi-solid | Texture only | 3 to 4 years | Moderate |
| Solid | No, like paint | 4 to 5 years | Hard — it peels |
There is a real trade buried in that last column. Solid stain lasts longest but fails by peeling rather than fading, which means stripping or sanding before you can recoat. Semi-transparent wears away gradually and can simply be cleaned and recoated. Going from semi-transparent to solid is easy; going back is a weekend with a sander. That is worth more thought than the extra year or two of life.
Prep, timing and the water test
- Clean and let it dry completely. Most stains will not penetrate damp or dirty wood, and 48 hours of dry weather after washing is a reasonable minimum.
- Do the water test. Sprinkle water on the boards: if it soaks in within a minute, the wood is ready. If it beads, an existing finish is still working and new stain will sit on top and stay tacky.
- New pressure-treated lumber needs to wait. It arrives saturated from the treatment process, and it can take several weeks to several months before it will accept stain. The water test is the arbiter, not the calendar.
- Stain between 50 and 90°F, out of direct midday sun. Hot boards flash-dry the stain before it penetrates, which leaves lap marks.
- Check the forecast for 24 to 48 hours. Rain on fresh stain means starting again.
- Work in full board lengths end to end, never stopping mid-board, or the overlap will show as a dark line forever.
On whether to apply two coats: many penetrating stains are formulated for one, and a second coat that the wood cannot absorb stays sticky and attracts dirt. Bare, thirsty wood and solid stains usually want two. Follow the can rather than the instinct that more is better.
How this deck stain calculator works out its numbers
Stain volume is area ÷ 250 ft² per gallon, per coat, reported to one decimal place. Waste defaults to 0 because stain is measured by absorption rather than cut from a sheet.
- 250 ft²/gal is a mid-range figure. Actual coverage runs 150 to 400 depending on wood porosity, product opacity and application method. Rough or weathered wood can take twice what smooth new lumber does, so treat the output as a starting point.
- Deck surface only. Railings, balusters and stairs are not included; add about 20% to the area you enter, or more for turned spindles.
- One coat is shown. Double it if you are applying two, which many stains do not need.
- For a fence, double the height you enter so both faces are counted, then judge coverage against the rough sawn figure rather than the smooth one.
- Product longevity figures are typical US ranges for exposed horizontal surfaces and vary widely with climate, sun exposure and traffic.
Reviewed September 2026.
Figures reviewed . Every worked example on this page is checked against the calculator above.
Deck Stain Calculator: frequently asked questions
How much does a gallon of deck stain cover?
250 ft² per coat is a reasonable planning figure. Smooth new wood stretches to 300 to 400 ft², while weathered or rough sawn boards drop to 150 to 250 — roughly half. Judge by how thirsty your wood is, not by the can.
How much stain do I need for a 12x16 deck?
About 0.8 gallons per coat for the deck surface alone, so buy 1 gallon. Add roughly 20% for railings, balusters and stairs, and double it if you are applying two coats.
How much stain for a 100 foot fence?
About 4.8 gallons per coat on smooth timber, or 6.9 gallons on rough sawn. A 100 ft fence at 6 ft tall is 1,200 ft² once you count both sides, which is the part most people forget to budget for.
Do I need two coats of stain?
Often not. Many penetrating stains are formulated for a single coat, and a second one the wood cannot absorb stays tacky and collects dirt. Bare thirsty wood and solid stains usually do want two. Follow the can.
How do I know if my deck is ready to stain?
Sprinkle water on it. If it soaks in within a minute the wood is ready; if it beads, an existing finish is still working and new stain will sit on the surface. Allow 48 hours of dry weather after washing.
Can I stain new pressure-treated wood?
Not immediately. It arrives saturated from the treatment and may need several weeks to several months to dry out enough to accept stain. Use the water test rather than a fixed waiting period.
Should I use semi-transparent or solid stain?
Semi-transparent for most decks. Solid lasts a year or two longer but fails by peeling rather than fading, so recoating means stripping or sanding. Going from semi-transparent to solid is easy; reversing it is a weekend with a sander.
How often should I re-stain a deck?
Every 1 to 3 years for horizontal surfaces taking sun and traffic, and longer for railings. Clear sealers need it annually and solid stains last 4 to 5 years. Recoat when water stops beading on the boards.