Bags of Crushed Stone for a 20x18 Patio
How many bags of crushed stone 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 crushed stone in 50-pound bags instead, figure about 187 bags, since crushed stone weighs roughly 104 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 | 63 |
| 2 in | 60.0 | 120 | 125 |
| 3 in | 90.0 | 180 | 187 |
| 4 in | 120.0 | 240 | 249 |
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 4.7 tons. At this size, a bulk delivery usually beats a cart full of bags once you count trips. Compare the bag price × 180 against a bulk quote for 5.1 tons delivered.
About crushed stone
Most quarries sell crushed stone by a size number or a screen size. Clean crushed stone drains well; stone with fines packs harder but sheds water more slowly.
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.
When to choose crushed stone
Works well for:
- Driveway top courses and parking pads
- Shed and hot tub bases
- Backfill behind walls when a clean size is used
Less suited to:
- Barefoot areas, since angular stone is rough
- Play areas
- Places that need a smooth rolling surface for wheels
Quick reference numbers
- Per inch over 100 sq ft: about 0.43 tons of crushed stone (0.31 cubic yards).
- Per inch over 1,000 sq ft: about 4.3 tons.
- Another size for comparison: a 10x20 area at 2 inches takes about 1.7 tons.
- Weight used here: about 1.4 tons per cubic yard.
Mistakes that throw off the order
- Forgetting that compaction shrinks loose material. A loose 4-inch spread of a dense-graded stone may finish closer to 3 inches after rolling.
- Ordering exactly the math. Uneven ground and spillage nearly always need a little more than the flat calculation.
- 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.
Questions people ask
How many bags of crushed stone for a 20x18 patio?
About 180 bags of 0.5 cubic feet at 3 inches deep.
How many 50 lb bags of crushed stone for 20x18?
About 187 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
- How Much Does a Ton of Crushed Stone Cover?
- Tons to Cubic Yards for Gravel: Conversion Chart
- How Much Does a Ton of Gravel Cover? Depth Chart
- Bags of Crushed Stone for a 20x14 Patio
- Bags of Crushed Stone for a 20x16 Patio
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