Gravel Calculator

Gravel is a loose mixture of rock fragments formed as a result of erosion. Along with sand and crushed stone, it is one of the most widely used construction materials in the world, and it has plenty of uses outside construction as well.

Rock fragments are classified by the size of the individual pieces. Sand is finer than gravel, gravel is finer than cobbles, and cobbles are finer than boulders. On the Udden-Wentworth scale used by geologists in the US, granular gravel runs 2-4 mm in diameter and pebble gravel 4-64 mm; the international standard ISO 14688 classifies gravel as fine (2.0-6.3 mm), medium (6.3-20 mm), or coarse (20-63 mm).

How much gravel do I need?

First work out the volume the gravel must fill: the area to be covered multiplied by the desired depth. The ideal depth depends on the application, but a minimum of 2-4 inches of gravel is a workable baseline. Once the volume is known, multiplying by the density of the gravel type gives the mass needed. Note that the price estimate here covers materials only - labor, delivery, and other project costs are not included.

What is gravel used for?

Construction. Almost half of the gravel produced in the US is used as aggregate for concrete. Gravel and sand also go into road construction and road bases, mixing with asphalt, construction fill, and products such as pipes, bricks, and concrete blocks. Gravel surfaces are common for driveways and walkways, and gravel is widely used for drainage because it forms a solid foundation while leaving cracks and spaces that let water through.

Landscaping and decoration. Gravel comes in many shapes, sizes, and colors, so it is used as decoration and as a functional border - around flower gardens, along walkways and driveways, or as a patio base. It can also substitute for organic mulch: it is more durable, needs less replacement, and is less likely to be moved around by the weather, while still protecting the soil.

Water treatment and agriculture. Gravel filters are one step in water treatment, trapping suspended solids that cannot physically pass through (they do not decontaminate water). Certain gravels, such as limestone and chalk, are ground into agricultural lime to reduce soil acidity, and ground gravel is also fed to poultry as a mineral source that helps them break down food.

Types of gravel

Bank gravel (bank run or river run) is found next to rivers and streams and mixes large and small rock fragments with sand and clay. It drains very well, helps prevent erosion, and is often used to fill gaps in the landscape or as a foundation for concrete. River stone is among the largest gravel types - smooth, naturally eroded stone used decoratively, for example lining ponds, creeks, and water features.

Pea gravel is a small, inexpensive gravel named for its pea-like size, used in road and driveway aggregate, concrete, landscaping, and aquariums. Crushed stone is made by mechanically crushing rock - usually limestone, dolomite, or granite - so it has rougher surfaces and sharper edges than eroded gravel; it is a standard concrete aggregate and road surface, though the sharp edges make it less pleasant for walkways.

Pay gravel (pay dirt) is distinguished not by its rock but by its content: significant concentrations of precious metals such as gold. It is rarely used for anything other than gold panning.