How Much Gravel Under a 20x20 Deck?
A 20 by 20 foot deck covers 400 square feet. At 3 inches of gravel, plan on 3.70 cubic yards, or about 5.2 tons, which answers how much gravel under a 20x20 deck.
Volume and tonnage calculator →The math
- Area: 400.0 sq ft.
- Depth in feet: 3 ÷ 12 = 0.250 ft.
- Cubic yards: 400.0 × 0.250 ÷ 27 = 3.70 yd³.
- Tons: × about 1.4 tons per yard = 5.2 tons.
The gravel calculator does this for any size.
Related: How Much Crushed Stone Under a 20x20 Deck?
Gravel needed by depth
| Depth | Cubic yards | Tons of gravel | Tons +10% |
|---|---|---|---|
| 2 in | 2.47 | 3.5 | 3.8 |
| 3 in | 3.70 | 5.2 | 5.7 |
| 4 in | 4.94 | 6.9 | 7.6 |
| 6 in | 7.41 | 10.4 | 11.4 |
Building the deck base
Gravel under a deck blocks weeds, keeps the ground from turning to mud and lets water drain. Lay landscape fabric first, then about 2 to 3 inches of stone; there is no need to compact it the way you would a driveway base.
Related: How Much Pea Gravel Under a 20x20 Deck?
Prep
Remove sod and roots, level the area and slope it slightly for drainage. Install edging so the stone stays inside the footprint.
Ordering and delivery
Small dump trucks commonly carry around 5 to 10 tons and tri-axles more, but loads vary by truck and state, so ask the yard what fits in one trip. Gravel is a broad label, so confirm whether the yard means crushed or rounded stone and whether it carries fines. Round up by about 10 percent for compaction and uneven ground.
Common mistakes
The most frequent problem is ordering for the finished depth without allowing for compaction, which can shrink a loose layer by 10 to 20 percent. Another is skipping fabric on soft soil and watching the stone vanish into the mud over the first wet season. Spreading everything in one thick layer instead of compacted lifts also leaves a soft, rutted surface.
Planning the cost
Stone is usually priced per ton or per cubic yard, and delivery is often a separate charge based on distance. A full truckload can cost less per ton than a partial one, so it can pay to combine projects. Ask whether the quote includes tax, delivery and any small-load fee before you compare yards.
Questions people ask
How many tons of gravel under a 20x20 deck?
About 5.2 tons at 3 inches deep.
How many yards of gravel under a 20x20 deck?
About 3.70 cubic yards.
How many tons of gravel are in a cubic yard?
Roughly 1.4 tons for planning, but suppliers vary with stone size and moisture.
Should I put landscape fabric under the stone?
On soft or clay soil, a woven geotextile keeps stone from sinking into the dirt and makes the layer last longer.
Related guides
- Gravel Under a Deck: Weeds, Drainage, and Depth
- How Much Does a Ton of Gravel Cover? Depth Chart
- Tons to Cubic Yards for Gravel: Conversion Chart
- Crushed Stone vs Gravel: Differences and Best Uses
- Geotextile Fabric for Driveways: Woven vs Nonwoven and How Much You Need
- Compacting a Driveway Gravel Base in Lifts
- How Much #57 Stone Under a 16x20 Deck?
- How Much Pea Gravel Under a 16x20 Deck?
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