One fence and one deck, measured once and ordered once. The job below uses a 120-foot fence, a 16-by-20-foot deck floor, a 5-step stair, and 28 feet of railing, and it ends with a whole-can order for each surface line, with every division shown.
How much stain does this job need?
At the TWP two-coat average of 100 to 125 ft² per gallon, the fence needs 12 to 15 gallons and the deck needs 6 to 9 gallons. The two lines add to 18 to 24 gallons only when the fence and the deck use the same product and color. When the products differ, the lines stay separate and no combined total is ordered.
Write the fence gallons, the deck floor gallons, the stair gallons, and the railing gallons on separate lines, each with its area and rate. A single job total cannot be re-checked line by line at the store.
What are the measured areas?
The areas come from the measurement guide. The fence is 120 linear feet at 6 feet high, stained on both sides. The deck floor is 16 by 20 feet, the stair line in the deck total is 30 ft² for one 5-step stair, and the railing is a planning line from the trade-guide rule of 10 to 15 ft² per linear foot.
| Line | Measurement | Area |
|---|---|---|
| Fence, one side | 120 ft × 6 ft | 720 ft² |
| Fence, both sides | 720 ft² × 2 sides | 1,440 ft² (133.78 m²) |
| Deck floor | 16 ft × 20 ft | 320 ft² |
| Stairs | One 5-step stair line | 30 ft² |
| Deck floor plus stairs | 320 ft² + 30 ft² | 350 ft² (32.52 m²) |
| Railing, planning line | 28 ft × 10 to 15 ft² per linear foot | 280 to 420 ft² (26.01 to 39.02 m²) |
| Deck total | 350 ft² + 280 to 420 ft² | 630 to 770 ft² (58.53 to 71.54 m²) |
How do you turn each area into gallons?
Gallons for one line = stainable area ÷ label coverage rate
A rate range gives a gallon range. Divide by the high rate for the low gallon figure and by the low rate for the high gallon figure, because the low end of the rate range sets the high end of the order. The TWP two-coat average of 100 to 125 ft² per gallon applies to every line below, since the whole job is ordered on that one product record.
| Line | Division | Gallons before rounding | Order |
|---|---|---|---|
| Fence, both sides | 1,440 ÷ 125 to 1,440 ÷ 100 | 11.52 to 14.4 | 12 to 15 gallons |
| Deck floor plus stairs | 350 ÷ 125 to 350 ÷ 100 | 2.8 to 3.5 | 3 to 4 gallons |
| Railing, planning line | 280 ÷ 125 to 420 ÷ 100 | 2.24 to 4.2 | 3 to 5 gallons |
| Deck total | 3 to 4 plus 3 to 5 | 6 to 9 gallons |
Each line rounds up on its own. The fence line rounds from 11.52 to 14.4 gallons up to 12 to 15 gallons, and the deck total comes from adding the two rounded deck lines, 3 to 4 plus 3 to 5, which gives 6 to 9 gallons.
How do you turn gallons into cans?
TWP lists its stain in 1-gallon and 5-gallon sizes, and Sherwin-Williams lists SuperDeck in 1-gallon and 5-gallon options, so those two sizes are the working pair here. Confirm the sizes your product is sold in before you use them, because sizes vary by brand and store.
| Line | Gallons | With 5-gallon pails | All 1-gallon cans |
|---|---|---|---|
| Fence | 12 to 15 | 2 pails plus 2 to 5 cans | 12 to 15 cans |
| Deck total | 6 to 9 | 1 pail plus 1 to 4 cans | 6 to 9 cans |
| Job total, same product and color only | 18 to 24 | 3 pails plus 3 to 9 cans | 18 to 24 cans |
The job total is a shopping convenience, not a planning line. The fence gallons and the deck gallons are counted separately first, and they are added only when the product and the color match. A gallon counted for the fence cannot cover the deck when the products differ.
How do you check the order before buying?
Multiply the ordered gallons back by the rate and confirm the result covers the area. For the fence, 12 gallons × 125 ft² per gallon = 1,500 ft², which covers 1,440 ft², and 15 gallons × 100 ft² per gallon = 1,500 ft², which also covers 1,440 ft². Both ends of the order pass the check.
The same check catches a rounded-down order. At the low rate of 100 ft² per gallon, 14 gallons cover only 1,400 ft², which falls 40 ft² short of the fence. That is why 14.4 gallons rounds up to 15 gallons rather than down to 14 gallons: rounding down buys a shortfall.
What changes when only one fence side is stained?
Stain one side only when the other side belongs to a neighbour or is deliberately left unstained, and record that choice beside the total. The fence area drops to 720 ft², and the fence order becomes 720 ÷ 125 = 5.76, rounded up to 6 gallons, to 720 ÷ 100 = 7.2, rounded up to 8 gallons.
The deck order does not change, so the job total for the same product and color becomes 6 to 8 plus 6 to 9, which is 12 to 17 gallons. The one-side choice removes 6 to 7 gallons from the fence line, and that single choice is the most common reason a fence order comes up short when it is missed.
What changes on rough wood?
Use the same 350 ft² deck floor plus stairs area with the Cabot semi-transparent record, which calls for one coat. On smooth wood at 250 to 350 ft² per gallon, the order is 350 ÷ 350 = 1.0 to 350 ÷ 250 = 1.4, rounded up to 1 to 2 gallons. On rough wood at 100 to 200 ft² per gallon, the same area needs 350 ÷ 200 = 1.75 to 350 ÷ 100 = 3.5, rounded up to 2 to 4 gallons.
Rough wood roughly doubles the order on the same area, and the Cabot line is a one-coat product while the TWP job above is a two-coat job. Do not mix the two product records in one line: the coat count, the rate, and the product name all belong on the line they came from.
What does the metric cross-check show?
The metric column records the same areas for a reader working in square metres, using 1 ft² = 0.09290304 m². The combined job area is 2,070 to 2,210 ft², which is 192.31 to 205.32 m². The metric figures are a record cross-check only: they restate the areas, and the gallon order above is unchanged.
Common mistakes in a worked example
- Counting one fence side and ordering 6 to 8 gallons for a two-side job that needs 12 to 15 gallons.
- Using the TWP first-coat rate of 150 to 200 ft² per gallon for both coats, which gives 8 to 10 gallons for the fence instead of 12 to 15 gallons.
- Rounding 14.4 gallons down to 14 gallons, which covers only 1,400 ft² at the low rate.
- Adding fence and deck gallons that use different products or colors into one order total.
- Leaving railing and stairs out of the deck total and treating the 320 ft² floor as the whole deck.
- Using a smooth-wood rate on rough-sawn boards, which roughly halves the order on the same area.
- Recording one combined gallon total with no area and no rate beside it, so no one can re-check it.
Safety and professional scope
A worked example does not select the stain, the preparation method, or the application method. Follow the product label for surface preparation, temperature limits, recoat timing, ventilation, cleanup, and disposal, and follow the project safety plan for work at height and on wet or uneven ground. Check local VOC rules and any project specification before buying, and bring in a qualified professional when the structure, the old coating, or the preparation step is outside a standard stain job.
Sources and scope
- TWP, deck stain calculator: deck area as flooring plus railing plus steps; fence as length × height × 2; TWP 100 and 1500 Series first-coat and two-coat coverage figures.
- TWP, Semi-Solid Pro-Series product page: gallon sizes of 1 and 5, coverage 150-250 ft² per gallon for that line.
- Cabot Semi-Transparent Deck and Siding Stain, Do it Best product record: 250-350 ft² per gallon smooth wood, 100-200 ft² per gallon rough wood, one-coat application.
- Angi, How Much Stain Do I Need For My Deck: floor length × width plus side pieces, railings, and stairs; common coverage 150-225 ft² per gallon.
- Angi, How Much Stain Do I Need For My Fence: length × height per side, both sides × 2.
- NIST Handbook 44, 2026 Appendix C: square-foot to square-metre relationship.
Scope: the example turns stated areas and one product record into whole-can orders. It does not measure the area, choose the stain, or approve surface preparation. The selected product's current label controls the coverage rate, coat count, container sizes, and final order quantity.
Review responsibility: Saleem Sial owns the published calculation, source, and editorial checks. Waseem Sial, External Reviewer and Engineer, remains listed for ongoing external review; no completed external-review date is claimed.
Next, measure the job with the fence and deck measurement guide, turn your own areas into cans with the fence and deck stain ordering guide, choose the product with the fence and deck stain guide, avoid the common fence and deck stain mistakes, or return to the Paint Calculator with the measured areas from this page.
