Square balusters
Twenty balusters, each 3 ft long and 1.5 in wide. Count the four long faces; add ends separately if you coat them.
20 × 3 ft × (1.5 ÷ 12) ft × 4 faces = 30 sq ftFree deck stain quantity & purchase planner
Deck Stain Calculator
How much stain will your deck really need? Count the surfaces you plan to coat, use the coverage on your product label, and compare whole cans or pails before you buy.
- Count the actual coated faces.
- Use your product’s coat coverage.
- Print or download your worksheet.
Deck stain purchase worksheet
bizntools.com/home-projects/deck-stain-calculator
Your stain order
Updates as you editEnter surface measurements and label coverage.
A purchase plan, coat by coat
Get the gallons your surfaces need, then compare whole cans or pails at your prices.
Measurements and prices stay in this tab.
Check the numbers
How to calculate deck stain quantities
Add the coated areas, then divide the total square feet by the first-coat coverage. For a two-coat product, calculate the second coat with its own coverage rate. Combine the gallons, add any allowance you choose, and only then round up to whole containers. Use the same product and color across the surfaces in one calculation.
Rectangle area: Length (ft) × width (ft)
Repeated equal faces: Length (ft) × width (in) ÷ 12 × pieces × equal faces
Two-coat volume: Area ÷ first-coat coverage + area ÷ second-coat coverage
Containers: Round up(total gallons with allowance ÷ container gallons)
Measure once. Make the basis clear.
Deck stain coverage and surface measurements
Start with the exact product label
One coat at 250 square feet per gallon is a different purchase from two coats at 250 and 500. Keep those rates separate. Surface texture, preparation and application affect the coverage you get.
| Coat | Published sq ft / US gal | Example input |
|---|---|---|
| First | 250–300 | 250 |
| Second | 500–600 | 500 |
The preset uses the lower endpoints to plan for more material. That is a planning choice, not a guaranteed coverage result. For a different stain, enter its own rates and required coat count.
Railing area is more than a single rectangle
Measure rails, balusters, posts and stairs as the faces you will actually coat. Repeated-piece mode works well for equal board faces. A square baluster has four equal long faces; a rectangular post may need two separate pairs. Add end faces only if they are part of the job.
For stain sold in liters, first use matching coverage and container units converted to US gallons. Do not enter a liter coverage figure as square feet per gallon.
Put a tape measure to the right faces
How to measure deck railings, posts and stairs
A 16 × 12 ft deck starts with 192 sq ft of top surface. The examples below add 88 sq ft if all four groups are included, for 280 sq ft in total. Use your actual dimensions and count each face once. Open “Need help measuring rails or steps?” above to add any group to your calculation.
Rectangular rails
Two 12 ft rails with measured 3.5 × 1.5 in sections. Separate the wide and narrow faces so gaps never become painted area.
2 × 12 ft × [(3.5 + 1.5) ÷ 12] ft × 2 = 20 sq ftSquare posts
Four exposed posts, each 3 ft high and actually 3.5 in wide. Count only accessible coated faces, not hidden or buried parts.
4 × 3 ft × (3.5 ÷ 12) ft × 4 faces = 14 sq ftStair treads & risers
Four 4 ft-wide steps: 11 in tread tops and 7 in riser fronts. These rows omit undersides, edges and stringers; add them if included.
4 × 4 ft × [(11 + 7) ÷ 12] ft = 24 sq ftAt the named example rates of 250 sq ft per gallon for the first coat and 500 for the second, 280 sq ft needs 1.68 US gallons before allowance. The product label decides the coat count and coverage; these dimensions do not.
Use your own deck measurements ↑Worked examples, not market quotes
Deck stain quantity and cost examples
A 16 × 12 ft deck, two coats
The deck top is 192 square feet. With label coverage of 250 square feet per gallon for the first coat and 500 for the second, it needs 0.768 + 0.384 = 1.152 US gallons before allowance. Buy two one-gallon cans. These are the lower coverage endpoints of BEHR No. 5077’s published ranges, not rates for every stain.
- Coated area
- 192 sq ft
- First + second coat
- 1.152 US gal
- Whole one-gallon cans
- 2
Include railing faces without counting empty space
Twenty square balusters, each three feet long and 1.5 inches wide, have 20 × 3 × 1.5 ÷ 12 × 4 = 30 square feet across their four long faces. Enter rails and posts separately; this does not count the baluster ends or the gaps between them.
- Balusters
- 20 pieces
- Equal long faces
- 4 per piece
- Additional coated area
- 30 sq ft
The bigger pail is not always the cheaper purchase
For a 1.152-gallon requirement, two one-gallon cans at $40 cost $80. One five-gallon pail at $150 costs more and leaves 3.848 gallons. Compare the complete purchase rather than the price per gallon alone. These prices are examples.
- Two one-gallon cans
- $80
- One five-gallon pail
- $150
- Smaller cans save
- $70
Questions before you finish
Deck stain calculator questions
How many square feet does a gallon of deck stain cover?
There is no single coverage rate for every deck stain. BEHR No. 5077 lists 250–300 square feet per gallon for its first coat and 500–600 for its second. Your stain can differ. Read the exact label, including the coat and surface conditions, then enter those figures.
Do I need one coat or two?
Follow the chosen product’s instructions. Some products require two thin coats; others are designed for one. The calculator starts without a coverage assumption and lets you enter one or two coats. The named BEHR example sets two because that product requires them.
Should I count the gaps between deck boards?
Measure the faces you actually coat. A simple deck rectangle includes narrow gaps, so it is a practical top-area approximation. For a more detailed count, enter boards in repeated-piece mode using actual board width, length and count. Add exposed edges separately if they will be coated.
How do I include railings and stairs?
Use the measurement examples to add balusters, rails, posts, or stairs, then replace their sample sizes with your measurements. Add a row for each group of equal faces. For square balusters, enter actual width, length, count and the number of long faces to coat. For treads and risers, enter their measured rectangles separately. Do not substitute the entire railing envelope when you want actual component area.
Should I use the low or high end of the coverage range?
A lower square-foot coverage number gives a larger purchase estimate. Use the rate appropriate to your surface and the label. The named preset uses the lower endpoints, but porosity, texture, preparation and application can still change real consumption.
Can I estimate fence stain here too?
Yes, if it uses the same product and coat system. Enter each measured coated face or repeated board group. Count both sides only when both will be coated, and run a separate calculation for a different color or product.
Why calculate gallons before rounding the cans?
Rounding each surface or coat first can buy unnecessary containers. This tool adds all surfaces and required coats, applies your allowance once, and then rounds the total up to each container size.
Assumptions and sources
See the calculation basis and references
- All volumes are US liquid gallons; 1 US gallon is about 3.785 liters. The calculator does not mix US and Imperial gallon coverage.
- Each surface receives the same product and coat system. Run different stains, colors or coating systems separately.
- Rectangle dimensions describe actual coated faces. Repeated-piece mode uses a width in inches and counts equal long faces only. For unequal post faces or end faces, add separate rows.
- Coverage and coat count come from your exact product label. The BEHR button is a clearly named example, not a recommendation or a live product database.
- The optional allowance is applied once to pooled gallons. A label rate that already includes material loss should not receive the same allowance twice.
- Each option is a complete purchase using one container size. Prices exclude tax, tools, cleaning supplies and labor. No automatic mixed-size optimization or application specification is claimed.
BEHR PREMIUM No. 5077 product instructions — Primary manufacturer source for the named example: two thin coats and distinct first/second coverage ranges. Checked 18 October 2026.
Cabot stain calculator — Manufacturer guidance to check the selected product label when estimating quantities. No Cabot rate is hardcoded.