How Much Road Base for a 20x40 Driveway?
How much road base for a 20x40 driveway: at 4 inches deep you need about 9.88 cubic yards, which is roughly 14.8 tons at 1.5 tons per yard. The driveway covers 800 square feet, so every inch of depth adds about 2.47 yards.
Volume and tonnage calculator →The math for a 20x40 driveway
- 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 is meant to be compacted at close to the right moisture. Dry base rock does not lock up well; a light spray of water before rolling helps. Weight per yard is a planning number; the scale ticket at the yard is the real one.
Preparing the driveway
Strip sod and soft topsoil, grade for drainage and compact the subgrade before any stone goes down. Gravel drives last longer with a compacted base layer under the top stone and a slight crown so water runs off. Since the driveway carries car and truck traffic, 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. 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 driveway 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
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 10x20 area at 3 inches takes about 2.8 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.
- Mixing up cubic yards and tons. Yards are volume, tons are weight; convert with the product’s weight per yard.
- Skipping drainage. Water sitting under any surface softens the base and leads to ruts and potholes.
- Measuring only the main rectangle. Aprons, turnouts and curved edges add real square footage.
Questions people ask
How many tons of road base for a 20x40 driveway?
About 14.8 tons at 4 inches deep, or 16.3 tons with 10 percent extra.
How many cubic yards is a 20x40 driveway 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 driveway?
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 Driveway?
- How Much Road Base for a 20x35 Driveway?
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