Gravel Calculator: Cubic Yards and Tons
Almost every slab on this site sits on a compacted gravel or crushed stone base — and the base is its own order, sold by the cubic yard or by the ton. Enter the area and depth to get both numbers, updated live as you type. The default below is the base for a 10×20 slab.
Before the allowance: 66.7 ft³ (2.47 yd³, 3.46 tons).
Gravel Yardage Table: Common Bases and Driveways
Exact volumes before any compaction cushion — add about 10% to the number you order. Tons use the standard conversion of 1.4 tons per cubic yard for gravel and crushed stone.
| Area | Depth | Volume | Cubic yards | Tons |
|---|---|---|---|---|
| 10 × 10 ft | 2 in | 16.7 ft³ | 0.62 yd³ | 0.86 |
| 10 × 10 ft | 4 in | 33.3 ft³ | 1.23 yd³ | 1.73 |
| 10 × 10 ft | 6 in | 50.0 ft³ | 1.85 yd³ | 2.59 |
| 10 × 20 ft | 4 in | 66.7 ft³ | 2.47 yd³ | 3.46 |
| 10 × 20 ft | 6 in | 100.0 ft³ | 3.70 yd³ | 5.19 |
| 12 × 12 ft | 4 in | 48.0 ft³ | 1.78 yd³ | 2.49 |
| 12 × 20 ft | 4 in | 80.0 ft³ | 2.96 yd³ | 4.15 |
| 12 × 20 ft | 6 in | 120.0 ft³ | 4.44 yd³ | 6.22 |
| 20 × 20 ft | 4 in | 133.3 ft³ | 4.94 yd³ | 6.91 |
How deep should the base be? 4 inches of compacted crushed stone is the standard base under a residential slab — it drains, it levels, and it keeps the slab from sitting in mud. Driveways and soft or clay soil call for 6 inches. Walkways and light patios can get away with 2–3 inches. Whatever the depth, that is the compacted depth: order loose material a little deep, spread it, and compact in lifts of about 2 inches loose at a time.
How the Math Works
Gravel is the same box math as a slab — length × width × depth — with one extra step: converting volume into weight, because many yards sell stone by the ton.
- Convert depth: divide inches by 12. (4 in = 0.333 ft.)
- Multiply: length × width × depth in feet = cubic feet.
- Cubic yards: divide cubic feet by 27.
- Tons: multiply cubic yards by 1.4. A cubic yard of gravel or crushed stone weighs about 1.4 tons (roughly 2,800 lb).
- Add the cushion: multiply by 1.10 for compaction and spillage.
Volume (ft³) = L × W × (D ÷ 12) · Tons = (ft³ ÷ 27) × 1.4
Worked example, a 10 × 20 ft base at 4 in: 10 × 20 × (4 ÷ 12) = 66.7 ft³, which is 66.7 ÷ 27 = 2.47 yd³, and 2.47 × 1.4 = 3.46 tons. With the 10% cushion: 2.72 yd³, or 3.80 tons — the numbers in the calculator above.
About that 1.4 figure: it is the standard planning conversion for gravel and crushed stone, but density varies with rock type, size, and moisture — real loads run about 1.3 to 1.5 tons per cubic yard. If your yard sells by the ton, order the tonnage; if they sell by the yard, order the yardage; either way the cushion absorbs the difference. Coverage shortcut: one cubic yard covers about 81 ft² at 4 in deep, and one ton covers about 58 ft² at the same depth.
Which stone? For a slab base you want crushed stone with fines (often sold as ¾ in crusher run, road base, or Class 2 base) — the angular pieces and fine particles lock together when compacted. Round pea gravel does not compact; it rolls under load like ball bearings and is a finish material, not a base.
Pouring the Slab on Top?
The base is only half the order. Once it is spread and compacted, the concrete that goes on it is figured with the main calculator — or skip straight to the guide for your size: 10×10 slab, 10×20 slab, 12×12 slab, 12×20 slab.
Gravel Calculator FAQ
How much gravel do I need under a 10×20 slab?
At the standard 4 in base depth: 2.47 yd³ (about 3.46 tons) exactly, and you should order about 2.72 yd³ or 3.80 tons to cover compaction and spillage. On soft or clay soil, go 6 in deep instead: 3.70 yd³, about 5.19 tons before the cushion.
How many tons are in a cubic yard of gravel?
About 1.4 tons. One cubic yard of gravel or crushed stone weighs roughly 2,800 lb, though the real figure runs 1.3 to 1.5 tons depending on rock type, stone size, and how wet the pile is. The 1.4 conversion is the standard number suppliers and estimators plan with.
How much area does a ton of gravel cover?
At 4 in deep, one ton covers about 58 ft², and one cubic yard covers about 81 ft². At 2 in deep those numbers double: roughly 116 ft² per ton and 162 ft² per yard. Depth is the lever — halving the depth doubles the coverage.
Should I buy gravel by the ton or by the cubic yard?
Whichever your local yard sells — the material is the same, and the calculator gives you both numbers. Bulk delivery beats bagged stone on any job over about a yard: a 10 × 20 base at 4 in would take well over a hundred 0.5 ft³ bags. Bagged gravel only makes sense for very small areas or where a truck cannot dump.
Estimates Only
Results are planning estimates. Actual gravel needs vary with ground conditions, excavation accuracy, and how much the material compacts. The 1.4 tons per cubic yard conversion is the standard planning figure for gravel and crushed stone; actual density runs about 1.3–1.5 tons per cubic yard. Always order a little extra — a second delivery fee costs more than a small surplus. For structural work (foundations, load-bearing footings, retaining walls), consult a licensed professional and follow your local building code.