How Much Road Base for a 12x40 Driveway?
A 12 by 40 foot driveway is 480 square feet. How much road base for a 12x40 driveway depends on depth: at 4 inches it is about 5.93 cubic yards or 8.9 tons. Suppliers usually sell by the ton, so the tonnage is the number to give them.
Volume and tonnage calculator →The math for a 12x40 driveway
- 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 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. If the yard sells by the cubic yard instead of the ton, use the cubic-yard column directly.
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. 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 driveway as firm ground allows.
Where road base fits
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 10x20 area at 2 inches takes about 1.9 tons.
- Weight used here: about 1.5 tons per cubic yard.
Where estimates go wrong
- Assuming every supplier uses the same weight. Two yards selling the same product name can quote different tons per yard.
- Ignoring the base. A thin surface layer over soft soil fails early no matter how much material is on top.
- Forgetting that compaction shrinks loose material. A loose 4-inch spread of a dense-graded stone may finish closer to 3 inches after rolling.
- Using inches as if they were feet. Depth has to be divided by 12 before you multiply; skipping that step inflates the order twelvefold.
Questions people ask
How many tons of road base for a 12x40 driveway?
About 8.9 tons at 4 inches deep, or 9.8 tons with 10 percent extra.
How many cubic yards is a 12x40 driveway 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 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 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 Driveway?
- How Much Road Base for a 12x35 Driveway?
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