Stain Calculator
Estimate stain gallons for wood surfaces by area and coverage rate, with waste built in.
Your Stain Estimate
- Measure the surface — use the length and width of the area you plan to stain (deck floor, fence section, etc.).
- Choose coverage rate — rough wood absorbs more stain; smooth wood spreads further per gallon.
- Set waste — include extra for rails, edges, and brush/roller loss.
- Round up — stain is sold in whole containers, and color consistency is easier when purchased together.
How Much Stain Do I Need?
Stain is estimated from surface area and the product's coverage rate. Coverage varies widely because rough or weathered wood absorbs more, while smooth or previously sealed wood can spread farther per gallon.
To estimate stain, compute area (length × width), apply a waste factor, then divide by the coverage rate. If you are staining rails or multiple faces (like fence pickets), include those surfaces in your total area or increase the waste factor.
Quick Reference: Gallons by Area
Coverage Tips (What Changes the Number)
Rough-sawn lumber, old decking, and end-grain soak up more stain. Rails, balusters, and edges add a surprising amount of surface area even when the footprint looks small. If you are applying multiple coats, multiply the gallons estimate by the number of coats.
Typical Coverage Ranges
Gallons Needed by Deck and Fence Size
Common deck and fence sizes with gallons needed for one coat at 150 ft²/gal (rough wood) and 250 ft²/gal (smooth or previously stained):
| Project | Size | 1 coat @ 150 ft²/gal | 1 coat @ 250 ft²/gal | 2 coats @ 150 ft²/gal |
|---|---|---|---|---|
| Small deck | 100 ft² | 1 gal | 1 gal | 2 gal |
| Medium deck | 200 ft² | 2 gal | 1 gal | 4 gal |
| Large deck | 400 ft² | 3 gal | 2 gal | 6 gal |
| Very large deck | 600 ft² | 4 gal | 3 gal | 8 gal |
| 6-ft privacy fence (50 lin ft) | 600 ft² | 4 gal | 3 gal | 8 gal |
| 6-ft privacy fence (100 lin ft) | 1,200 ft² | 8 gal | 5 gal | 16 gal |
| Split-rail fence (100 lin ft) | 400 ft² | 3 gal | 2 gal | 6 gal |
Rails, balusters, and spindles add 20–30% more surface area beyond the deck boards. For a complete deck with railing, add 25% to your board-area estimate before calculating gallons.
Formulas Used in This Calculator
Coverage calculation:
1 = Adjusted area = base area × (1 + waste %)
2 = Gallons needed = adjusted area ÷ coverage rate (round up)
3 = For multiple coats: total gallons = gallons × number of coats
Related Calculators
Stain coverage rates vary by porosity — always test a patch first. Browse the surface calculator collection.
Frequently Asked Questions
How many square feet does a gallon of stain cover?
It depends on the product and the wood. A common planning range is 150–250 ft² per gallon. Rough or weathered wood often needs more stain.
Should I count rails and balusters?
If you can estimate their surface area, yes. Otherwise, increase waste to 15–20% to account for rails, edges, and brush/roller loss.
What is the difference between solid and semi-transparent stain?
Solid stain acts more like paint and fully covers the wood grain. Semi-transparent lets the grain show through and is better for newer wood in good condition. Transparent stains offer minimal color and work only on new or recently stripped wood. Coverage rates are similar, but solid stains often require fewer coats on weathered surfaces.
How many coats of stain do I need?
Most decks and fences need 2 coats on bare or stripped wood, and 1–2 coats for maintenance re-staining. Always follow the product label. Some penetrating stains specify not to apply a second coat until the first has dried, which can take 24–48 hours depending on humidity and temperature.
Does this include multiple coats?
The calculator estimates a single coat. For two coats, multiply the gallons result by 2.