Crush Rock Calculator: Volume & Tons Needed

A crush rock calculator works out how much crushed stone you need for a project: you enter the area’s length, width, and depth, and it returns the volume in cubic feet, cubic yards, and the weight in tons. It uses the standard formula Volume = Length × Width × Depth, then multiplies by the rock’s density (typically 1.4 tons per cubic yard for crushed stone) to give the tonnage. This page explains the math, how to use the calculator, and what to watch out for so you order the right amount the first time.

Formula

The calculator uses the basic volume formula for a rectangular prism:

Volume (cubic feet) = Length (ft) × Width (ft) × Depth (ft)

Since depth is usually measured in inches, convert it to feet first: Depth (ft) = Depth (in) ÷ 12

Then convert cubic feet to cubic yards (the unit used for ordering): Cubic yards = Cubic feet ÷ 27

Finally, convert volume to weight using the density of crushed stone. A typical value is 1.4 tons per cubic yard (about 2,800 lb per cubic yard), but this varies with rock type and moisture. The formula becomes:

Tons = Cubic yards × 1.4

If you prefer metric: Volume (m³) = Length (m) × Width (m) × Depth (m), and weight (tonnes) = Volume (m³) × 1.6 (approximate density of crushed stone in tonnes/m³).

Worked Example

Using the default values from the calculator: Length = 10 ft, Width = 10 ft, Depth = 4 in.

1. Convert depth to feet: 4 in ÷ 12 = 0.3333 ft
2. Volume in cubic feet: 10 × 10 × 0.3333 = 33.33 cu ft
3. Convert to cubic yards: 33.33 ÷ 27 = 1.2346 cu yd
4. Weight in tons: 1.2346 × 1.4 = 1.7284 tons

The calculator rounds to two decimals, giving 33.33 cu ft, 1.23 cu yd, and 1.73 tons. So for a 10×10 ft area with a 4-inch layer, you’d order about 1.75 tons (or 2 tons if you round up to account for compaction).

How to Use the Calculator

Enter three numbers:

• Length – the longest side of the area in feet (or meters if using metric).
• Width – the shorter side in the same unit.
• Depth – how thick you want the layer, usually in inches (or centimeters).

The calculator assumes a rectangular area. For irregular shapes, break the area into rectangles, calculate each, and add the results. If your area is a circle (like a fire pit base), use the formula for a cylinder: Volume = π × (radius²) × depth, then convert to tons using the same density.

Choosing the Right Depth

Depth depends on the project:

• Pathway (walking): 2–3 inches
• Driveway (cars): 4–6 inches (over a geotextile fabric)
• Base for pavers or concrete: 4–6 inches of compacted crushed stone
• French drain or trench: 6–12 inches, depending on pipe size

For driveways, consider that the stone compacts by about 10–15% under rolling. Many contractors order 10–15% extra to account for this. The calculator does not include compaction, so add that manually if needed.

Common Mistakes and Misconceptions

Mistake 1: Mixing units. If you measure length in feet and depth in inches, you must convert depth to feet. Failing to do so will make your volume 12 times too large.

Mistake 2: Using the wrong density. Crushed stone density varies: limestone is about 1.4 tons/cu yd, granite is about 1.5, and gravel with sand can be 1.6–1.8. The calculator uses 1.4 as a general average. Check with your supplier for the exact density of the material you’re buying.

Mistake 3: Forgetting compaction. Freshly placed crushed stone settles. If you order exactly the calculated volume, you’ll end up short after compaction. Add 10–15% or order by weight with a note that you need that volume after compaction.

Mistake 4: Assuming 1 ton = 1 cubic yard. A ton is a weight, a cubic yard is a volume. Crushed stone weighs about 1.4 tons per cubic yard, so 1 ton is only about 0.71 cubic yards. Always convert using density.

How to Read the Results

The calculator gives three numbers:

• Cubic feet – useful for small amounts or if you’re comparing with bagged stone (which is often sold by cubic foot).
• Cubic yards – the standard unit for ordering bulk crushed stone. Most suppliers sell by the cubic yard.
• Tons – the weight, which is how the stone is actually weighed when delivered (truck scales).

When you call a supplier, you can order either by cubic yards or by tons. If you order by tons, use the calculator’s tons output. If you order by cubic yards, use the cubic yards output. Be aware that some suppliers have a minimum order (often 1–2 cubic yards) and charge delivery fees.

Limits of the Formula

The formula assumes a perfectly flat, rectangular area with uniform depth. In reality, the ground may be uneven, and you might need more stone to fill low spots. Also, the density of 1.4 tons/cu yd is an average; actual density depends on the rock type (limestone, granite, trap rock), the size of the crushed pieces (e.g., 3/4-inch vs. 1-1/2-inch), and moisture content. For critical projects, ask your supplier for the exact density of the product you’re buying.

Finally, this calculator is for estimation. Always verify with your supplier and consider ordering a little extra to account for spillage and compaction.

Frequently Asked Questions

How many cubic yards are in a ton of crushed stone? Since crushed stone averages 1.4 tons per cubic yard, one ton is about 0.71 cubic yards (1 ÷ 1.4). For a more exact figure, divide 1 by the actual density of your material.

What depth of crushed stone do I need for a patio? For a patio that will have pavers on top, you typically need 4–6 inches of compacted crushed stone as a base. For a simple gravel patio with no pavers, 3–4 inches is enough. Always check local building codes for specific requirements.

Can I use this calculator for gravel or pea gravel? Yes, the volume calculation is the same. The only difference is the density: pea gravel is about 1.4 tons/cu yd, while crushed stone with fines can be up to 1.6 tons/cu yd. Adjust the density in the formula if needed.

Why does my supplier sell by the ton instead of cubic yard? Because trucks are weighed on scales, weight is the most accurate way to measure a load. Volume can vary with compaction and moisture. However, most suppliers can quote you in either unit; use the calculator’s tons output to compare prices.

How much area does one ton of crushed stone cover? At a 4-inch depth, one ton (about 0.71 cu yd) covers roughly 57 square feet (0.71 × 27 / (4/12) = 57.8 sq ft). At 2 inches deep, it covers about 115 sq ft. Use the calculator in reverse: enter the area you want and adjust the depth to see how many tons you need.

Should I order extra crushed stone? Yes, it’s wise to order 10–15% extra to account for compaction, uneven ground, and spillage. For example, if the calculator says 1.73 tons, order about 2 tons. This is especially important for driveways where compaction is significant.

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in l | Length | ft | 10 | 0
in w | Width | ft | 10 | 0
in d | Depth | in | 4 | 0
out cu_ft | Volume | cu ft | l * w * (d / 12) | 2
out cu_yd | Volume | cu yd | (l * w * (d / 12)) / 27 | 2
out tons | Weight | tons | ((l * w * (d / 12)) / 27) * 1.4 | 2