CONSTRUCTION CALCULATOR
Deck Stain Calculator
Estimate how many gallons of deck stain you need for a rectangular deck surface, including coats and a waste allowance.
Tool presets, labelled as such: coverage per gallon is a tool preset of 200 sq ft/gal and waste is a tool preset of 10%. Both are editable in the tool.
Planning estimate only. Check the stain product label for its coverage, and measure the deck surface before ordering.
Estimate stain
RESULTS
Gallons to buy: 3 gallons
Exact gallons: 2.112 gallons
Deck area: 192 sq ft
Gallons before waste: 1.92 gallons
Waste gallons: 0.192 gallons
Results update as you type or change a value. No form submission is used to recalculate.
How to use this calculator
Enter the deck length and width in feet, the number of coats, the coverage per gallon, and the waste percentage. The tool updates the results as you type or change a value. For a deck that is not a rectangle, split it into rectangles, run each part through the tool, and add the results.
Worked example – checked against the tool
For a 12 ft by 16 ft deck with 2 coats, coverage of 200 sq ft per gallon, and 10% waste: Step 1 – Area: 12 x 16 = 192 sq ft. Step 2 – Gallons before waste: 192 x 2 / 200 = 1.92 gallons. Step 3 – Exact gallons with waste: 1.92 x (1 + 10/100) = 2.112 gallons. Step 4 – Gallons to buy: ceil(2.112) = 3 gallons.
Data table
| Deck size | Coats | Coverage (sq ft/gal) | Waste | Exact gallons | Gallons to buy |
|---|---|---|---|---|---|
| 10 ft x 10 ft | 2 | 200 | 10% | 1.1 | 2 |
| 12 ft x 16 ft | 2 | 200 | 10% | 2.112 | 3 |
| 16 ft x 20 ft | 2 | 200 | 10% | 3.52 | 4 |
| 20 ft x 12 ft | 3 | 200 | 10% | 3.96 | 4 |
| 10 ft x 12 ft | 1 | 200 | 10% | 0.66 | 1 |
Frequently asked questions
How many gallons of stain do I need for a 12 by 16 deck with 2 coats?
At the tool presets of 200 sq ft per gallon and 10% waste, a 192 sq ft deck needs 2.112 exact gallons, so buy 3 gallons.
What coverage per gallon should I use?
Start with the tool preset of 200 sq ft per gallon, then change it to the coverage stated on your stain product label, because coverage varies by product and wood condition.
What does the waste allowance cover?
The tool preset of 10% waste allows for absorption, spills, and application variation. Increase it for rough or weathered wood, and decrease it only if the product label supports a lower allowance.
Does this calculator include railings, spindles, or stairs?
No. It covers the flat deck surface only. Measure railings, spindles, and stairs separately and add their stain separately.
Can I use this calculator for a fence?
No. A fence has different surfaces and coverage. Use the Fence Cost Calculator for an adjacent fence as a separate scope.
Why are gallons to buy rounded up?
Stain is bought in whole gallons, so the tool rounds the exact gallons up to the next whole gallon with ceil().
Method note
Area = length x width. Gallons exact = area x coats / coverage x (1 + waste/100). Gallons to buy = ceil(exact). Coverage and waste are tool presets, labelled as such in the tool, and both are editable. This is a planning estimate, not a product-specific guarantee.
Related calculators
- Deck Cost Calculator – for the total project budget for the same deck.
- Deck Board Calculator – for board quantities for the deck area.
- Fence Cost Calculator – for an adjacent fence as a separate scope.