How Much Does 21 Tons of Road Base Cover?
How much does 21 tons of road base cover depends on how deep you spread it. At about 1.5 tons per cubic yard, 21 tons is roughly 14.0 cubic yards. Spread 6 inches deep, that covers about 756 square feet. Halve the depth and you roughly double the area.
Volume and tonnage calculator →How the coverage is figured
- Tons to cubic yards: 21 ÷ 1.5 = 14.0 yd³.
- Cubic yards to cubic feet: × 27 = 378 cu ft.
- Divide by depth in feet: at 6 inches (0.500 ft), 378 ÷ 0.500 = 756 sq ft.
Coverage of 21 tons at different depths
| Depth | Square feet covered | Square yards |
|---|---|---|
| 4 in | 1,134 | 126 |
| 6 in | 756 | 84 |
| 8 in | 567 | 63 |
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 runs about 1.4 to 1.65 compacted tons per cubic yard, so treat the table as a planning range rather than an exact figure.
Putting 21 tons to use
For delivery, 21 tons means multiple trips or a larger truck. Ask the supplier how they will split it. Spread from the pile with a loader, skid steer or wheelbarrow, then rake to depth before compacting if the material calls for it.
- Check depth as you go. Stakes marked at the target depth help keep the spread even.
- Expect some loss. Compaction and uneven ground use more than the flat-math figure. Keep about 10 percent in reserve.
- Ask about moisture. Wet material weighs more, so a ton of it covers less.
To run your own numbers, use the volume and tonnage calculator.
Where road base fits
Works well for:
- Base under asphalt and concrete
- Gravel roads and drives
- Equipment and shed pads
Think twice 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.
Mistakes that throw off the order
- Using inches as if they were feet. Depth has to be divided by 12 before you multiply; skipping that step inflates the order twelvefold.
- 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.
- Forgetting that compaction shrinks loose material. A loose 4-inch spread of a dense-graded stone may finish closer to 3 inches after rolling.
Questions people ask
How many cubic yards is 21 tons of road base?
About 14.0 cubic yards at 1.5 tons per yard.
How many square feet does 21 tons of road base cover at 6 inches?
About 756 square feet.
How many square feet does 21 tons cover at 4 inches?
About 1,134 square feet.
How much does a yard of road base weigh?
About 1.4 to 1.65 compacted tons.
Will 21 tons fit in one truck?
It depends on the truck. Single-axle dump trucks often carry under 10 tons and tandems around 13 to 16; your supplier will know their limits.
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 19 Tons of Road Base Cover?
- How Much Does 20 Tons of Road Base Cover?
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