Estimate gravel and landscape fabric for the area beneath an attached or freestanding deck.
Your estimate
YOU NEED
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≈ —
—Net landscape fabric coverage
—Effective gravel area
—Calculated geometric volume
Estimate breakdown
Deck footprint
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Effective gravel area
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Base volume
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Allowance
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Final order volume
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Fabric roll plan
Cut list—
Purchase quantity—
Total cut material—
Enter valid dimensions and roll details to compare both strip directions.
Weight uses the selected approximate gravel density. Confirm material and ordering quantities with your supplier.
How to use this calculator
Enter the deck dimensions, choose whether one long side is attached to the house, and select a gravel depth and edge extension. The estimate updates as you change the inputs; the optional allowance affects gravel quantity, not fabric area.
How much gravel should go under a deck?
Depth depends on drainage, grade and site conditions; there is no universal depth for every deck. Use the 2 in starting value only if it suits your project, and check with a qualified installer or local requirements.
Why use gravel under a deck?
Gravel may help with drainage, mud reduction and a cleaner surface. Landscape fabric can help suppress weeds and separate gravel from soil, but gravel or fabric is not required for every deck.
Common deck sizes
Planning references use an attached deck, no gravel extension, 2 in gravel depth and no allowance. Values are generated using the same calculation as the estimate above.
Deck size
Gravel area
Volume at 2 in
Approx. weight
8 × 10 ft
80.00 sq ft
0.49 yd³
0.67 US tons
10 × 12 ft
120.00 sq ft
0.74 yd³
1.00 US tons
12 × 16 ft
192.00 sq ft
1.19 yd³
1.60 US tons
16 × 20 ft
320.00 sq ft
1.98 yd³
2.66 US tons
Worked fabric roll example
For an attached 12 × 16 ft deck with no edge extension, 2 in of gravel and no allowance, the area is 192 sq ft and the gravel estimate is 1.19 yd³. Suppose the fabric comes in 4 × 50 ft rolls and its product instructions call for a 6 in side overlap. The no-join layout cuts five 12 ft strips, or 60 linear ft and 240 sq ft of fabric.
One 50 ft roll yields only four full 12 ft strips, so this example needs two whole rolls. Dividing the 192 sq ft net coverage by the 200 sq ft printed on one roll would miss the overlap and the strip cuts. Enter your own roll dimensions and manufacturer-specified overlap in the optional fabric roll plan above. Posts, obstructions, edge fixing and lengthwise joins are outside this example.
Under deck gravel questions
How deep should gravel be under a deck?
There is no single required depth for every site. Use a depth that suits drainage and grade conditions, and follow local project requirements or a qualified installer’s advice.
Do I need landscape fabric under deck gravel?
Landscape fabric is optional. It can help separate gravel from soil and reduce weed growth, but it is not a substitute for drainage planning or every site-specific ground treatment.
Should gravel extend beyond the deck?
Some projects use a gravel margin to cover the surrounding drip area. This calculator lets you choose no extension, 6 inches or 12 inches; check clearances and drainage at your site.
Does this calculator include compaction?
No. The allowance is a user-selected extra for uneven ground and measurement differences. It is not a compaction factor.