This deck & fence stain calculator works out the gallons of stain to buy for your deck size — or your fence length and height — by coats and coverage. No sign-up. The working is shown under every number.
Quick example: a 16 × 12 ft deck with 2 coats of stain at 200 sq ft per gallon coverage needs 2 gallons — $76.00 at the example prices.
| Item | Buy | Cost |
|---|---|---|
| Estimated total | $0.00 |
Gallons are rounded up to whole gallons. Keep the part-used gallon for touch-ups — stain colour varies slightly between batches, so buy all you need in one trip.
Estimate only — not a guarantee. Mistakes are possible, so always check the quantities with your supplier or a builder before you buy or build.
Work out the fence area first: length × height × the number of sides you are staining. A 100 ft long, 6 ft high fence stained on both sides is 1,200 sq ft; at the standard 200 sq ft per gallon coverage that is 6 gallons for one coat — the same figure published fence-stain examples give. This calculator does the area for you in fence mode.
The floor of a 16 × 12 ft deck is 192 sq ft. At 200 sq ft per gallon, one coat takes about 1 gallon and the usual two-coat job takes 2 gallons (1.92 worked out exactly, rounded up to whole gallons). Railings and steps add area — the calculator adds about 3 sq ft for every foot of railing and 4 sq ft per step if you enter them.
Manufacturers quote anywhere from about 150 to 300 sq ft per gallon. Smooth new wood drinks the least; rough, dry or weathered wood can pull coverage down toward 125–175 sq ft per gallon, and a first coat always drinks more than a second. This calculator starts at 200 sq ft per gallon — lower it toward 150 for old weathered wood so you do not run short mid-fence.
Two thin coats is the standard recommendation for decks and fences: the first seals the wood, the second evens the colour and adds the weather protection. One coat can look patchy within a season. Very weathered wood sometimes needs a third light coat on the worst boards — the calculator lets you set 1, 2 or 3 coats.
| Deck job | Area | Stain (exact) | Gallons to buy | Total |
|---|---|---|---|---|
| 12 × 12 ft deck | 144 sq ft | 1.44 gal | 2 | $76.00 |
| 16 × 12 ft deck | 192 sq ft | 1.92 gal | 2 | $76.00 |
| 16 × 12 ft deck + 24 ft of railing | 264 sq ft | 2.64 gal | 3 | $114.00 |
| 20 × 16 ft deck | 320 sq ft | 3.20 gal | 4 | $152.00 |
Railing area is counted at 3 sq ft per foot of railing (posts, rails and balusters together) and steps at 4 sq ft each. Gallons are rounded up to whole gallons — stain is normally sold by the gallon (and quart for touch-ups).
These figures are planning estimates only — not a guarantee and not professional advice. Mistakes are possible, including through an error in this calculator. Always check the quantities, sizes, spacings and depths with your supplier, a licensed builder, and your local building code before you buy materials or start work. The owner of this site accepts no responsibility or liability for any loss, cost, damage, injury, wasted material or failed inspection that results from using these estimates. Prices are examples to start from, not live prices or quotes.