How Much Road Base for a 18x20 Parking Pad?
A 18 by 20 foot parking pad is 360 square feet. How much road base for a 18x20 parking pad depends on depth: at 4 inches it is about 4.44 cubic yards or 6.7 tons. Suppliers usually sell by the ton, so the tonnage is the number to give them.
Volume and tonnage calculator →The math for a 18x20 parking pad
- Area: 18 × 20 = 360 sq ft.
- Depth in feet: 4 ÷ 12 = 0.333 ft.
- Cubic feet: 360 × 0.333 = 120.0 cu ft.
- Cubic yards: ÷ 27 = 4.44 yd³.
- Tons: × 1.5 = 6.7 tons.
The volume and tonnage calculator does this for any size.
Road base needed by depth
| Depth | Cubic yards | Tons (approx.) | Tons +10% |
|---|---|---|---|
| 4 in | 4.44 | 6.7 | 7.3 |
| 6 in | 6.67 | 10.0 | 11.0 |
| 8 in | 8.89 | 13.3 | 14.7 |
About road base
Road base (also called base rock, ABC, or Class 2 base in different states) is a graded mix of stone and fines made to compact into a load-bearing layer. Weight per yard is a planning number; the scale ticket at the yard is the real one.
Preparing the parking pad
Dig out organic soil, compact the subgrade and set an edge so the stone does not migrate onto the lawn. A pad that holds parked weight for long periods benefits from a dense base under the surface stone. This parking pad sees parked vehicles, so match the depth to that load rather than to the minimum.
Ordering tips
- Round up. Compaction and uneven ground eat material. Adding about 10 percent is common.
- Delivery size. 7.3 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 parking pad as firm ground allows.
When to choose road base
Best suited to:
- Base under asphalt and concrete
- Gravel roads and drives
- Equipment and shed pads
Less suited to:
- Drainage layers
- Decorative surfaces
- Surfaces that will stay uncompacted
Quick reference numbers
- Per inch over 100 sq ft: about 0.46 tons of road base (0.31 cubic yards).
- Per inch over 1,000 sq ft: about 4.6 tons.
- Another size for comparison: a 14x28 area at 4 inches takes about 7.3 tons.
- Weight used here: about 1.5 tons per cubic yard.
Mistakes that throw off the order
- Assuming every supplier uses the same weight. Two yards selling the same product name can quote different tons per yard.
- Using inches as if they were feet. Depth has to be divided by 12 before you multiply; skipping that step inflates the order twelvefold.
- Ignoring the base. A thin surface layer over soft soil fails early no matter how much material is on top.
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
Questions people ask
How many tons of road base for a 18x20 parking pad?
About 6.7 tons at 4 inches deep, or 7.3 tons with 10 percent extra.
How many cubic yards is a 18x20 parking pad at 4 inches?
About 4.44 cubic yards.
How much does a cubic yard of road base weigh?
Usually around 1.4 to 1.65 compacted tons, depending on stone size, fines and moisture.
How deep should road base be for a parking pad?
The table above shows 4 to 8 inches. Shallower depths suit top dressing; deeper depths suit new installs and heavier use.
How many square feet is 18x20?
360 square feet.
Related guides
- Crushed Stone vs Gravel: Differences and Best Uses
- 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 Road Base for a 16x40 Parking Pad?
- How Much Road Base for a 16x50 Parking Pad?
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