How Much Road Base for a 12x40 Parking Pad?
How much road base for a 12x40 parking pad: at 4 inches deep you need about 5.93 cubic yards, which is roughly 8.9 tons at 1.5 tons per yard. The parking pad covers 480 square feet, so every inch of depth adds about 1.48 yards.
Volume and tonnage calculator →The math for a 12x40 parking pad
- Area: 12 × 40 = 480 sq ft.
- Depth in feet: 4 ÷ 12 = 0.333 ft.
- Cubic feet: 480 × 0.333 = 160.0 cu ft.
- Cubic yards: ÷ 27 = 5.93 yd³.
- Tons: × 1.5 = 8.9 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 | 5.93 | 8.9 | 9.8 |
| 6 in | 8.89 | 13.3 | 14.7 |
| 8 in | 11.85 | 17.8 | 19.6 |
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. Since the parking pad carries parked vehicles, a little extra depth is cheap insurance.
Ordering tips
- Round up. Compaction and uneven ground eat material. Adding about 10 percent is common.
- Delivery size. 9.8 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.
Good and poor uses for road base
Good uses:
- 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 15x30 area at 3 inches takes about 6.2 tons.
- Weight used here: about 1.5 tons per cubic yard.
Common estimating mistakes
- 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.
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- 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 tons of road base for a 12x40 parking pad?
About 8.9 tons at 4 inches deep, or 9.8 tons with 10 percent extra.
How many cubic yards is a 12x40 parking pad at 4 inches?
About 5.93 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 12x40?
480 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 12x30 Parking Pad?
- How Much Road Base for a 12x36 Parking Pad?
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