Gravel Calculator

This calculator estimates how much gravel it takes to cover an area at the depth you want, and what that will cost. Enter the area directly, or give the length and width of a rectangle or the diameter of a circle and it works the area out for you. Covering 200 m² to a depth of 3 cm takes 6,000 liters of gravel, which is 6 m³ or 7.85 cubic yards, and weighs about 10,080 kg.

What gravel is

Gravel is a loose mixture of rock fragments produced by erosion. It is used across construction alongside other rock fragments such as sand and crushed stone, though it has plenty of uses outside building work too.

Rock fragments are classified by the size of the individual pieces in the aggregate. Sand is made of fragments smaller than gravel, gravel is smaller than cobbles, and cobbles are smaller than boulders. The exact boundaries depend on which standard you follow. Two are in common use: the Udden-Wentworth scale, used by geologists in the US, and the international standard ISO 14688. Udden-Wentworth calls a fragment granular gravel at 2 to 4 mm (0.079 to 0.157 in) and pebble gravel at 4 to 66 mm (0.2 to 2.5 in). ISO 14688-1:2002 splits gravel into fine (2.0 to 6.3 mm), medium (6.3 to 20 mm) and coarse (20 to 63 mm).

How much gravel do I need?

How much you need depends entirely on the project, and the calculator above is there to turn the specifics into a number. The price it gives covers materials only. Delivery, labour, edging and groundworks are all extra, and on a small job they often add up to more than the stone itself.

The method is the same whatever the project. Work out the area to be covered and decide on a depth. Multiplying the two gives the volume of gravel needed. Once you have the volume, the density of the type of gravel you are buying converts it into a weight, which is how most suppliers actually sell it.

Depth is the part people underestimate. A minimum of 2 to 4 inches is a workable baseline for most surfaces, but the right figure depends on what the surface has to carry.

Use	Typical depth
Decorative bed or border	2 in (5 cm)
Garden path, foot traffic	2 to 3 in (5 to 7.5 cm)
Driveway top layer	3 to 4 in (7.5 to 10 cm)
Driveway, full build over sub-base	8 to 12 in (20 to 30 cm) in layers
Drainage trench or French drain	Fill the trench

A driveway that takes vehicle weight is not a single layer. It is usually a coarse sub-base with a finer top layer over it, each compacted separately, and the calculator should be run once per layer.

A worked example

Take a driveway 20 ft long and 10 ft wide, topped up to 4 inches. The area is 200 ft², and 4 inches is a third of a foot, so the volume is 66.67 cubic feet. Divide by 27 to get 2.47 cubic yards, since a cubic yard is 3 × 3 × 3 feet. At the gravel density of 1,680 kg/m³ that comes to about 3,171 kg, or 3.5 short tons.

Then add for compaction. Gravel settles as it beds in and gets driven on, and the usual allowance is 10 to 20 percent on top of the calculated figure. At 15 percent the order becomes about 4 tons rather than 3.5. Running short in the middle of a job usually means a second delivery charge for a fraction of a load, so rounding up is the cheaper mistake.

Why the density matters

Volume tells you how much space the stone will fill. Weight is what you are charged for, and the two are connected by density, which varies more than people expect.

Material	Density (kg/m³)	Density (lb/ft³)
Gravel (0.2 to 2 in, or 0.5 to 5 cm)	1,680	104.9
Gravel with sand	1,920	119.9
Dry sand	1,602	100.0
Wet sand	1,922	120.0

Two things move these numbers. The first is packing: the same stone loose in a pile and compacted in place occupies different volumes, and the figures above are for material as delivered rather than after rolling. The second is water. Wet sand is roughly 20 percent heavier than dry sand for the same volume, which is why a load delivered after heavy rain can weigh noticeably more than the same load in a dry week. If you are buying by weight, that difference is money.

The calculator offers a custom density field for anything not in the list. Suppliers publish the figure for their own products, usually in kg/m³ or lb/ft³, and using theirs is always better than using a generic one.

Buying by volume or by weight

Bulk gravel is sold by the cubic yard in some places and by the ton in others, and the two are not interchangeable without the density. One cubic yard of gravel at 1,680 kg/m³ weighs about 1,284 kg, which is 2,832 lb or 1.42 short tons. Ordering "three yards" and "three tons" are different orders, and the gap is not small.

Watch the two kinds of ton as well. A short ton is 2,000 lb and is what a US supplier means. A metric ton is 1,000 kg, about 2,205 lb, and is what most of the rest of the world means. The calculator reports both.

Bagged gravel is priced per bag and suits small jobs. A garden path 10 m long and 1 m wide at 5 cm deep needs half a cubic meter, about 840 kg, which is 34 bags at 25 kg each. That is the point where bulk delivery starts to look better, since bagged stone typically costs several times as much per ton.

What gravel is used for

Gravel is a widely used commercial product, running from decorative use in a garden to road building. Billions of tons of sand and gravel are produced for construction worldwide every year.

Construction

Almost half the gravel produced in the US goes into concrete as aggregate. Construction aggregate is a broad category of rock fragments from medium to coarse, and besides sand and gravel it includes crushed stone, slag and recycled concrete. Gravel and sand are also used for road construction, mixed with asphalt, as construction fill, and in making pipes, bricks and concrete blocks.

Gravel makes roof coverings, walkways and driveways too. A mixture of sand and gravel goes into shingles; walkways are often a mix of gravel and stone; a driveway may be gravel alone or gravel with asphalt.

Drainage is another common use, in professional work and in back gardens alike, because gravel gives a solid base while leaving enough gaps between the pieces for water to pass through. That combination is hard to get from anything else at the price.

Landscaping and decoration

Gravel comes in a range of shapes, sizes and colours, so it is used decoratively as well as functionally, and it drains while it does it. It works as a border for a flower bed to hold back soil that might otherwise erode, as a patio base, or to line a walkway or driveway.

It also substitutes for organic mulch. Gravel lasts far longer than bark or straw and needs replacing much less often, while still shading the soil, holding heat and slowing evaporation. It is heavier than organic mulch too, so it stays where it was put instead of blowing or washing out of shape.

Water treatment and agriculture

Gravel is used in water filtration to remove suspended solids. A gravel filter does not decontaminate water. It is one step in a treatment process, and it only removes solid particles too large to pass through, so any contaminant that is dissolved rather than suspended goes straight through with the water.

Some gravels are ground for agricultural use. Limestone or chalk is pulverised into agricultural lime, a soil additive that reduces acidity to help crops grow. Ground gravel is also fed to poultry: chickens and turkeys need small stones and minerals in their diet to grind food down, since they have no teeth.

Types of gravel

Gravel is generally categorised by the size of the fragments and by how it was produced. Some definitions separate gravel from crushed stone on whether the pieces were mechanically crushed or worn down by natural erosion. Eroded gravel tends to be smoother and rounder, crushed stone rougher and sharper. The distinction is not always drawn, and since the same word covers several products it is worth being specific about which one you are ordering.

Bank gravel

Bank gravel, also called bank run or river run, is found beside rivers and streams. It is a mixture of large and small fragments with sand and clay in it. It drains well, which helps prevent soil erosion and lets plants root and grow, and it is typically used to fill gaps in a landscape or as a foundation under concrete.

River stone

River stone, or river rock, is among the largest gravels. River, creek and beach stones are all the same naturally eroded material. Their smooth surfaces and range of colours make them mostly decorative, used in landscaping or for lining ponds, creeks and water features, where their draining capacity also helps.

Pea gravel

Pea gravel takes its name from its size, close to a garden pea. It is one of the cheapest gravels, so it turns up almost everywhere: as aggregate in roads and driveways, in concrete, and around plants in landscaping, where its mix of chipped and rounded pieces gives colour and texture. It drains well and is common in aquariums. Its one weakness is that rounded stones roll, so on a slope or a driveway it migrates and needs edging to stay put.

Crushed stone

Crushed stone is a medium-sized gravel made by mechanically crushing rock, usually limestone, dolomite or granite. Some definitions exclude it from gravel entirely on the grounds that it is processed rather than naturally occurring. The practical difference is the shape: crushed faces and sharp edges, against the smooth rounded surface of eroded gravel.

Most crushed stone goes into concrete aggregate. Colours and textures vary with the parent rock, and it is sold in size grades. It is the usual choice for surfacing roads and driveways, because those angular faces interlock under load and the surface stays where it is put. That same sharpness makes it less pleasant underfoot, so it is used less for walkways and paths than smoother gravel.

Pay gravel

Pay gravel, or pay dirt, can be made of more or less any rock. What defines it is that it carries meaningful concentrations of a precious metal, usually gold. It is rarely used for anything other than panning, for the obvious reason.

Reading the results on this page

The panel gives volume first, in liters with cubic meters, cubic yards and cubic feet underneath, then weight in kilograms with metric tons, pounds and short tons. Between them they cover however your supplier quotes. The area is shown as well, which is the number to check first if the answer looks wrong, since an area unit set to square feet when you meant square meters is the most common slip. The step-by-step card shows the three multiplications behind the answer: area by depth for volume, volume by density for weight, and weight by price for cost.