How Much Road Base for a 20x40 Parking Pad?
How much road base for a 20x40 parking pad is a quick volume problem. 800 square feet at 4 inches comes to 9.88 cubic yards. Road base usually weighs about 1.4 to 1.65 compacted tons per cubic yard, so plan on roughly 14.8 tons.
Volume and tonnage calculator →The math for a 20x40 parking pad
- Area: 20 × 40 = 800 sq ft.
- Depth in feet: 4 ÷ 12 = 0.333 ft.
- Cubic feet: 800 × 0.333 = 266.7 cu ft.
- Cubic yards: ÷ 27 = 9.88 yd³.
- Tons: × 1.5 = 14.8 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 | 9.88 | 14.8 | 16.3 |
| 6 in | 14.81 | 22.2 | 24.4 |
| 8 in | 19.75 | 29.6 | 32.6 |
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. If the yard sells by the cubic yard instead of the ton, use the cubic-yard column directly.
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. 16.3 tons may take more than one 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.
Good and poor uses for road base
Best suited to:
- Base under asphalt and concrete
- Gravel roads and drives
- Equipment and shed pads
Poor fit for:
- 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 20x25 area at 4 inches takes about 9.3 tons.
- Weight used here: about 1.5 tons per cubic yard.
Mistakes that throw off the order
- Measuring only the main rectangle. Aprons, turnouts and curved edges add real square footage.
- Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- Ignoring the base. A thin surface layer over soft soil fails early no matter how much material is on top.
Questions people ask
How many tons of road base for a 20x40 parking pad?
About 14.8 tons at 4 inches deep, or 16.3 tons with 10 percent extra.
How many cubic yards is a 20x40 parking pad at 4 inches?
About 9.88 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 20x40?
800 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 20x30 Parking Pad?
- How Much Road Base for a 20x36 Parking Pad?
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