Bags of Pea Gravel for a 20x18 Patio
How many bags of pea gravel 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 pea gravel in 50-pound bags instead, figure about 187 bags, since pea gravel 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. Past about a yard, bulk is usually less work and often less money. Compare the bag price × 180 against a bulk quote for 5.1 tons delivered.
About pea gravel
Pea gravel is small, rounded stone, usually around 3/8 inch. It is comfortable to walk on and drains well, but it shifts under car tires and needs a solid edge to stay put.
Install tips 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 rake smooth; rounded stone will not 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.
Good and poor uses for pea gravel
Good uses:
- Patios, walkways and dog runs
- Play areas with proper depth and edging
- Drainage around foundations when sized properly
Poor fit for:
- Driveways and steep paths, where it rolls and ruts
- Under pavers as a base
- Areas without edging
Quick reference numbers
- Per inch over 100 sq ft: about 0.43 tons of pea gravel (0.31 cubic yards).
- Per inch over 1,000 sq ft: about 4.3 tons.
- Another size for comparison: a 12x24 area at 2 inches takes about 2.5 tons.
- Weight used here: about 1.4 tons per cubic yard.
Where estimates go wrong
- Ordering exactly the math. Uneven ground and spillage nearly always need a little more than the flat calculation.
- Measuring only the main rectangle. Aprons, turnouts and curved edges add real square footage.
- Forgetting that compaction shrinks loose material. A loose 4-inch spread of a dense-graded stone may finish closer to 3 inches after rolling.
- 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 pea gravel for a 20x18 patio?
About 180 bags of 0.5 cubic feet at 3 inches deep.
How many 50 lb bags of pea gravel 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 Gravel Cover? Depth Chart
- Tons to Cubic Yards for Gravel: Conversion Chart
- How Much Does a Ton of Gravel Cover? Depth Chart
- Bags of Pea Gravel for a 20x14 Patio
- Bags of Pea Gravel for a 20x16 Patio
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