How Much #57 Stone for a 20x18 Patio?
How much #57 stone for a 20x18 patio: at 3 inches deep you need about 3.33 cubic yards, which is roughly 4.5 tons at 1.35 tons per yard. The patio covers 360 square feet, so every inch of depth adds about 1.11 yards.
Volume and tonnage calculator →The math for a 20x18 patio
- Area: 20 × 18 = 360 sq ft.
- Depth in feet: 3 ÷ 12 = 0.250 ft.
- Cubic feet: 360 × 0.250 = 90.0 cu ft.
- Cubic yards: ÷ 27 = 3.33 yd³.
- Tons: × 1.35 = 4.5 tons.
The volume and tonnage calculator does this for any size.
#57 stone needed by depth
| Depth | Cubic yards | Tons (approx.) | Tons +10% |
|---|---|---|---|
| 2 in | 2.22 | 3.0 | 3.3 |
| 3 in | 3.33 | 4.5 | 5.0 |
| 4 in | 4.44 | 6.0 | 6.6 |
| 6 in | 6.67 | 9.0 | 9.9 |
About #57 stone
Since #57 is washed and open-graded, it moves a little underfoot. Many installers put it over a compacted base of a dense-graded stone rather than straight on soil. Weight per yard is a planning number; the scale ticket at the yard is the real one.
Preparing the patio
Remove sod, level the area with a slight slope away from the house, and lay landscape fabric if weeds are a concern. Edging keeps loose material inside the patio footprint. For foot traffic and furniture, the depths in the table above are a reasonable starting range.
Ordering tips
- Round up. Compaction and uneven ground eat material. Adding about 10 percent is common.
- Delivery size. 5.0 tons fits in a single typical dump truck load; small loads may carry a delivery fee. See how many tons of gravel in a dump truck.
- Bulk vs bags. At this size bulk delivery is usually the practical choice.
- Where it drops. Have the truck dump as close to the patio as firm ground allows.
When to choose #57 stone
Works well for:
- French drains and drainage layers
- The top course of a gravel driveway
- Under sheds where water needs to drain away
Think twice for:
- A standalone base, since it does not pack hard without fines
- Paver setting beds
- Walk paths meant for strollers or wheelchairs
Quick reference numbers
- Per inch over 100 sq ft: about 0.42 tons of #57 stone (0.31 cubic yards).
- Per inch over 1,000 sq ft: about 4.2 tons.
- Another size for comparison: a 12x24 area at 3 inches takes about 3.6 tons.
- Weight used here: about 1.35 tons per cubic yard.
Mistakes that throw off the order
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- Forgetting that compaction shrinks loose material. A loose 4-inch spread of a dense-graded stone may finish closer to 3 inches after rolling.
- Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
- Ordering exactly the math. Uneven ground and spillage nearly always need a little more than the flat calculation.
Questions people ask
How many tons of #57 stone for a 20x18 patio?
About 4.5 tons at 3 inches deep, or 5.0 tons with 10 percent extra.
How many cubic yards is a 20x18 patio at 3 inches?
About 3.33 cubic yards.
How much does a cubic yard of #57 stone weigh?
Usually around 1.3 to 1.45 tons, depending on stone size, fines and moisture.
How deep should #57 stone be for a patio?
The table above shows 2 to 6 inches. Shallower depths suit top dressing; deeper depths suit new installs and heavier use.
How many square feet is 20x18?
360 square feet.
Related guides
- Number 57 Stone: Size, Weight, Uses, and Coverage
- Tons to Cubic Yards for Gravel: Conversion Chart
- How Many Tons of Gravel in a Dump Truck? Loads and Coverage
- How Much Does a Ton of Gravel Cover? Depth Chart
- How Much #57 Stone for a 20x14 Patio?
- How Much #57 Stone for a 20x16 Patio?
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