Deck Stain Calculator
Gallons of stain for a deck, including railings and coats.
Total run of railing. Enter 0 for a ground-level deck without rails.
From the can. Use 150 to 200 for old or rough wood, 250 to 300 for smooth new wood.
You need
2.3 gallons
Buy 3 gallon(s). Leftover stain is useful for annual touch-ups.
- Deck surface
- 192 sq ft
- Railing surface
- 98 sq ft
- Total area to coat
- 580 sq ft
Estimates only. Verify quantities before ordering.
How this is calculated
Stainable area = (deck length x width) + (railing length x 3.5). Gallons = area x coats / coverage per gallon. The purchase figure rounds up to whole gallons.
Enter your deck's dimensions and the total length of railing, and this calculator estimates the stain you need. Railings are the part everyone underestimates: balusters, rails, and posts add a surprising amount of surface, so the calculator converts each linear foot of railing into about 3.5 square feet of stainable area.
Coverage varies more with stain than with paint. New, smooth wood might take 250 to 300 square feet per gallon, while old, weathered, or rough-sawn boards can drink stain at 150 square feet per gallon. The first coat always absorbs more than the second. Check the can and adjust the coverage field to match your product and the condition of your wood.
Stain for common deck sizes
Rows assume two coats at 250 sq ft per gallon, with a railing run typical for each deck size. Round up to whole gallons.
| Deck size | Gallons | Area to coat |
|---|---|---|
| 10 x 10 ft, 24 ft railing | 1.5 gallons | 368 sq ft |
| 12 x 12 ft, 28 ft railing | 1.9 gallons | 484 sq ft |
| 16 x 12 ft, 32 ft railing | 2.4 gallons | 608 sq ft |
| 20 x 14 ft, 40 ft railing | 3.4 gallons | 840 sq ft |
| 20 x 16 ft, 44 ft railing | 3.8 gallons | 948 sq ft |
Common questions
How many coats of deck stain do I need?
Transparent and semi-transparent penetrating stains usually take one to two thin coats; a second coat should go on before the first fully dries so it can still absorb. Solid stains behave more like paint and typically need two coats. Never build thick layers of penetrating stain, since the excess will not soak in and stays sticky.
How do I know when my deck needs re-staining?
Sprinkle water on the boards. If it beads up, the finish is still repelling water. If it soaks in and darkens the wood within a couple of minutes, the protection is gone and it is time to clean and re-stain. Most horizontal deck surfaces need re-coating every 2 to 3 years.
Do I have to strip the old stain first?
If you are re-coating with the same type and a similar or darker color, a thorough cleaning is usually enough. Switching from solid to transparent stain, or dealing with peeling, requires stripping or sanding back to bare wood, because transparent products cannot hide or bond over a failing solid film.
How long should a new deck dry before staining?
Pressure-treated lumber needs to dry out before it will accept stain, typically 1 to 3 months depending on climate and how wet the boards were at purchase. Use the water test: when droplets soak in rather than bead on the surface, the wood is ready.