Bags of Decomposed Granite for a 20x18 Patio
How many bags of decomposed granite for a 20x18 patio: at 3 inches deep you need about 90.0 cubic feet, which is 180 bags of the common 0.5 cubic foot size. If your store sells decomposed granite in 50-pound bags instead, figure about 180 bags, since decomposed granite weighs roughly 100 pounds per cubic foot.
Volume and tonnage calculator →Bag count by depth
| Depth | Cubic feet | 0.5 cu ft bags | 50 lb bags (approx.) |
|---|---|---|---|
| 1 in | 30.0 | 60 | 60 |
| 2 in | 60.0 | 120 | 120 |
| 3 in | 90.0 | 180 | 180 |
| 4 in | 120.0 | 240 | 240 |
How to figure it
- Area: 20 × 18 = 360 sq ft.
- Volume: 360 × (3 ÷ 12) = 90.0 cu ft.
- Bags: 90.0 ÷ 0.5 = 180 bags (round up).
Bags or bulk?
A cubic yard is 27 cubic feet, so 90.0 cubic feet is 3.33 yards, about 4.5 tons. Past about a yard, bulk is usually less work and often less money. Compare the bag price × 180 against a bulk quote for 5.0 tons delivered.
About decomposed granite
Decomposed granite (DG) is weathered granite broken into small particles and fines. It packs into a firm, natural-looking path surface, and stabilized versions include a binder.
Laying it down for a patio
- Dig and level. Remove sod and set the base slightly below the surrounding grade.
- Edge it. Steel, plastic or stone edging keeps material in place.
- Spread in layers. Rake to depth, then tamp or wet and compact.
- Buy a few extra. Grab 5 to 10 percent more bags for settling and touch-ups.
The volume and tonnage calculator handles other sizes and depths.
Where decomposed granite fits
Best suited to:
- Garden paths and patios with a natural look
- Around trees and in xeriscape designs
- Stabilized DG for accessible paths
Poor fit for:
- Steep grades without a stabilizer
- Areas right outside doors, since fines track in
- Driveways with heavy turning traffic
Quick reference numbers
- Per inch over 100 sq ft: about 0.42 tons of decomposed granite (0.31 cubic yards).
- Per inch over 1,000 sq ft: about 4.2 tons.
- Another size for comparison: a 14x28 area at 2 inches takes about 3.3 tons.
- Weight used here: about 1.35 tons per cubic yard.
Where estimates go wrong
- Measuring only the main rectangle. Aprons, turnouts and curved edges add real square footage.
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
- Assuming every supplier uses the same weight. Two yards selling the same product name can quote different tons per yard.
Questions people ask
How many bags of decomposed granite for a 20x18 patio?
About 180 bags of 0.5 cubic feet at 3 inches deep.
How many 50 lb bags of decomposed granite for 20x18?
About 180 bags at 3 inches.
How many 0.5 cubic foot bags are in a cubic yard?
54 bags.
How many cubic feet is a 20x18 patio at 3 inches?
About 90.0 cubic feet.
When does bulk make more sense?
Usually once the job passes about a cubic yard, or when you would need more than a few car trips.
Related guides
- Crushed Stone vs Gravel: Differences and Best Uses
- Tons to Cubic Yards for Gravel: Conversion Chart
- How Much Does a Ton of Gravel Cover? Depth Chart
- Bags of Decomposed Granite for a 20x14 Patio
- Bags of Decomposed Granite for a 20x16 Patio
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