# Rock Calculator

URL: https://speedycalculator.com/calculators/construction/rock/
Last updated: 2026-10-25

> The rock calculator works out how much crushed stone you need from the area and depth, in cubic yards, cubic metres, tons and tonnes, and estimates the cost from a price per ton or per cubic yard.

## Inputs

- Material
- Custom density (kg/m³, lb/ft³, g/cm³, lb/yd³)
- Area shape
- Length (or diameter) (ft, m, in, yd, cm)
- Width (ft, m, in, yd, cm)
- Depth (in, cm, mm, ft, m)
- Extra for waste and compaction (%)
- Priced by
- Price per weight (/US ton, /t, /lb, /kg)
- Price per volume (/yd³, /m³, /ft³)

## Results

- Area
- Volume needed
- Weight needed
- Estimated cost

## Formula

```
Volume = area × depth × (1 + waste)
Weight = volume × density
Cost = weight × price per ton (or volume × price per yd³)
```

## Explanation

Whether it is a load of crushed rock for a base, decorative stone for a garden or larger rock for erosion control, you need to know both the volume and the weight before calling the quarry. Different rocks have very different densities: basalt is about 20% heavier than limestone and lava rock is roughly half the weight of either.

### How to use the Rock Calculator

- **Material**
- **Custom density**
- **Area shape**
- **Length (or diameter)**
- **Width**
- **Depth**
- **Extra for waste and compaction**
- **Priced by**
- **Price per weight**
- **Price per volume**
- Every result field is editable: type into **Volume needed** or any other result and **Depth** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

The calculator finds the area of your rectangle, circle or triangle, multiplies it by the depth and adds the waste allowance to get the volume. Multiplying by the density of the chosen material gives the weight, and the price you enter turns either one into a cost.

### Densities used

Materialkg/m³lb/ft³US tons per yd³Crushed stone1,602100.01.35Granite, crushed1,650103.01.39Basalt, crushed1,954122.01.65Limestone, crushed1,55497.01.31Sandstone, broken1,51094.31.27River rock1,60099.91.35Pea gravel1,52094.91.28Lava rock80049.90.67Marble chips1,57098.01.32Rip rap / large rock1,700106.11.43

### Good to know

A U.S. (short) ton is 2,000 lb; a metric tonne is 1,000 kg (2,204.6 lb). Quarries in the U.S. sell by the short ton, so check which one your quote uses.

### Tips for an accurate estimate

- Sketch the job and split irregular areas into rectangles, circles and triangles before you measure.
- Add a waste allowance – typically 5–10% for simple layouts and 15–20% for diagonal, curved or heavily cut work.
- Check the coverage or yield printed on the product, because sizes and densities vary between manufacturers.
- Buy all units of a finished material (tile, brick, siding) from the same batch so colours match, and keep a few spares for repairs.
- Confirm local prices – quarry, lumber and steel prices vary widely by region and season.

### Common mistakes to avoid

- Ordering exactly the calculated amount with no allowance for breakage, offcuts and settlement.
- Forgetting to subtract doors, windows and other openings – or subtracting small ones that still need cutting around.
- Confusing US short tons (2,000 lb) with metric tonnes (1,000 kg) when comparing quotes.

### Inputs explained

FieldWhat to enterMaterialChoose one: Crushed stone, Granite, crushed, Basalt, crushed, Limestone, crushed …Custom densityUnits: kg/m³, lb/ft³, g/cm³, lb/yd³Area shapeChoose one: Rectangle / square, Circle (length = diameter), Triangle (length = base, width = height)Length (or diameter)Units: ft, m, in, yd, cmWidthUnits: ft, m, in, yd, cmDepthUnits: in, cm, mm, ft, mExtra for waste and compactionIn %Priced byChoose one: Weight (per ton / tonne), Volume (per yd³ / m³)Price per weightUnits: /US ton, /t, /lb, /kgPrice per volumeUnits: /yd³, /m³, /ft³

## Worked example

Inputs — Material: Crushed stone; Custom density: 1,600 kg/m³; Area shape: Rectangle / square; Length (or diameter): 20 ft; Width: 10 ft; Depth: 4 in; Extra for waste and compaction: 10 %; Priced by: Weight (per ton / tonne); Price per weight: $45 /US ton; Price per volume: $60 /yd³.

Results — Area = 200 ft²; **Volume needed = 2.716 yd³**; Weight needed = 3.667 US ton; Estimated cost = $165.02.

## FAQ

**How do I calculate how much rock I need?**
Multiply length × width × depth to get the volume, add 5–10%, then multiply by the rock's bulk density for the weight.

**How many tons of rock are in a cubic yard?**
Usually 1.2–1.5 US tons for crushed rock and about 0.7 tons for lava rock.

**What depth for a rock garden?**
2–3 in for decorative stone over landscape fabric.

**What formula does the Rock Calculator use?**
Volume = area × depth × (1 + waste).


## Sources

- [The Engineering ToolBox – Bulk densities of materials](https://www.engineeringtoolbox.com/density-materials-d_1652.html)