Gravel Calculator

How much gravel do I need?

The quantity of gravel you need is controlled by three things: the area you are covering, the finished depth of the gravel layer, and the bulk density of the material if you also need a weight estimate. The area and depth determine volume. Density converts that volume into tons or tonnes.

That distinction matters because gravel is commonly measured in cubic yards or cubic metres when you think about the space to fill, while a quarry, aggregate yard or landscape supplier may quote and deliver it by weight. A gravel calculator should therefore show both rather than pretending that a yard and a ton are interchangeable.

This calculator keeps the geometry and the weight conversion separate. First it works out the physical volume of the finished layer. Then it applies any order allowance you choose. Finally, it converts the order volume to weight using either a material planning density or the custom density you enter from your supplier.

Gravel calculator formulas

Rectangular area

For a rectangular driveway, path, pad or bed, multiply length by width to get area. Multiply area by depth to get volume.

When using feet for length and width and inches for depth, convert the depth to feet before calculating cubic feet:

There are 27 cubic feet in one cubic yard, so:

A convenient shortcut combines the depth and yard conversions:

The constant 324 comes from 12 inches per foot multiplied by 27 cubic feet per cubic yard.

Metric calculation

For metric projects, the geometry is more direct. If length and width are in metres and depth is in centimetres:

Weight from density

Volume alone does not tell you the weight. To estimate weight, multiply the order volume by the material's bulk density:

The density value is the least certain part of a typical gravel estimate. Gravel is not one uniform product: crushed stone, pea gravel, river rock and dense graded road base can have different bulk weights. Particle size distribution, how angular the stone is, void space, moisture and the supplier's specific source all affect the delivered weight. For a final order, use the density or conversion factor supplied for the actual product whenever you can.

What the order allowance does — and what it does not do

The optional order allowance simply increases the calculated material quantity by the percentage you enter. It is useful when you want a little extra for uneven subgrade, edge loss, spreading variation or minor spillage.

That separation is intentional. Many simple calculators combine "waste" and "compaction" into one unexplained number. That can be convenient, but it can also hide an assumption that is not valid for every project. SonoCalculator leaves the percentage under your control and labels it as an ordering allowance.

Choosing the right gravel depth

There is no single correct gravel depth for every project. Decorative gravel, a pedestrian path, a drainage trench and a vehicle-bearing base have different jobs. The right depth depends on the material size, subgrade, load, drainage, climate and whether the gravel is a surface layer or one layer in a larger construction system.

These ranges are for planning, not structural design. Highway and pavement guidance treats granular base as a load-bearing component and specifies material gradation and compaction in controlled layers. A residential landscape project does not need to imitate a highway specification, but the principle is useful: a structural gravel layer should be designed as a layer system, not just as a decorative blanket of stone.

Gravel density: why tons can only be estimated

A cubic yard is a volume. A ton is a weight. You cannot make an exact conversion from one to the other without knowing the bulk density of the actual material.

The calculator includes rounded planning densities so it can return a useful first estimate. They are deliberately editable. A supplier may give density in tons per cubic yard, pounds per cubic foot, kilograms per cubic metre or a simple "yards per ton" conversion for a particular product. Use the supplier's figure when available because it reflects the stone type, grading and source you are actually buying.

Loose gravel versus compacted aggregate

Bulk density also depends on the material condition. Loose stone in a stockpile or truck body contains voids between particles. A well-graded aggregate that is compacted into a base can rearrange and occupy less volume. Moisture can also increase delivered weight. That is why the most defensible workflow is:

• calculate the finished geometric volume required by the project;
• identify whether the layer will be loose, lightly settled or compacted to a specification;
• use the supplier or project conversion for that material condition;
• add a separate order allowance only for the uncertainty you actually want to cover.

How to measure a gravel project accurately

Rectangle or square

Measure the longest finished length and width of the area. Use the Length × width mode. If the edges vary, divide the project into smaller rectangles, calculate them separately and add the areas before using the Known area mode.

Known area

If you already have square footage or square metres from a site plan, survey, paving layout or another SonoCalculator tool, select Known area. This avoids re-entering dimensions and is useful for irregular projects that you have already broken into shapes.

Round area

For a circular gravel pad, fire-pit surround or round landscape bed, measure the finished diameter. The calculator uses:

Irregular areas

For an irregular path or curved bed, do not automatically multiply the maximum length by the maximum width; that can overstate the area substantially. Divide the shape into rectangles, triangles or simple sections, or use an accurately measured total area. If the path has a fairly consistent width, measuring centreline length and average width can also produce a practical estimate.

Worked example: 20 ft × 10 ft area at 4 inches deep

Suppose a project is 20 feet long, 10 feet wide and needs a finished gravel depth of 4 inches. First find the area:

Convert 4 inches to feet and calculate cubic feet:

Convert to cubic yards:

If you choose a 10% order allowance:

Using a planning density of 1.40 US tons per cubic yard:

The volume part of this example follows directly from the measurements. The 3.80-ton figure is an estimate because it depends on the density assumption. If the supplier gives you a different tons-per-yard figure, enter that number and the calculator will update the weight.

How many cubic yards of gravel do I need?

If you know the area in square feet, the fastest US-customary formula is:

These figures are theoretical volume before any order allowance and before any loose-to-compacted conversion that your particular project may require.

How much area does one cubic yard cover?

Coverage works in reverse: one cubic yard equals 27 cubic feet, so the shallower the layer, the more square feet it covers.

Coverage tables are useful for a quick reasonableness check, but they do not account for uneven grade, settlement, compaction, edge loss or a supplier's specific bulk density.

Gravel for driveways

A driveway estimate should usually be handled layer by layer. A gravel driveway may include a prepared subgrade, a coarse or dense-graded base/subbase, and a smaller surface aggregate. The total thickness that works in one location may be inadequate in another because soil strength, drainage, freeze-thaw conditions and vehicle loads differ.

For each layer, enter its own finished length, width and thickness and calculate the quantity separately. Do not calculate the full depth once and assume every layer uses the same material density or gradation. That approach is both more accurate for ordering and more useful when different materials have different prices.

Gravel for paths, patios and landscape beds

For a path or decorative bed, the measurement challenge is usually the shape rather than the weight. Measure the finished boundaries carefully, account for edging, and decide whether the depth is a decorative top layer or part of a base system.

If the project has a compacted aggregate base under pavers, calculate that base separately from bedding sand and the pavers themselves. If the project is decorative pea gravel or river rock, the selected particle size can change both appearance and practical coverage: large rounded stone may expose more voids, while smaller graded material can pack more tightly.

Gravel for drainage

Drainage projects need more than a generic depth recommendation. For a trench, the gravel volume depends on trench length, trench width and the portion of trench depth occupied by aggregate. A pipe also occupies space, so a highly precise drainage estimate can subtract the pipe volume from the gravel-filled cross-section.

For ordinary planning you can calculate the trench as a rectangular volume, then reduce the result if a large pipe or other component occupies a meaningful share. For engineered drainage, septic, retaining-wall drainage or foundation work, follow the applicable detail for aggregate type, filter fabric, pipe bedding and cover.

Estimating gravel cost

The calculator can estimate material cost when you enter a local price. Choose whether the supplier quoted a price per ton or per cubic yard. The calculation uses the order quantity after your allowance.

The result is a material-only estimate unless the price you enter already includes other charges. Delivery, minimum-load fees, tax, grading, excavation, geotextile, edging, equipment, labor and disposal are not automatically added.

For metric mode, the price basis changes to per tonne or per cubic metre. The currency symbol is intentionally generic; enter the amount in whichever currency your quote uses.

Bulk gravel versus bags

Small decorative jobs are often convenient to handle with bags because they are easy to transport and place. Larger areas are usually supplied in bulk. Bag sizes are not universal, so the safest bag calculation is based on the exact volume printed on the package:

Round bag quantities up to whole bags. If a product label gives coverage at a stated depth instead of bag volume, use that manufacturer's coverage figure because it is product-specific.

Common gravel estimating mistakes

• Mixing inches and feet without conversion. Four inches is one-third of a foot, not four feet.
• Treating a ton as a cubic yard. One measures weight and the other measures volume.
• Using one density for every gravel product. Bulk density varies by material, grading, void space, moisture and supplier.
• Using maximum length × maximum width for an irregular area. This can overestimate curved or tapered projects.
• Forgetting that a driveway is often layered. Calculate different aggregate layers separately.
• Adding an arbitrary compaction percentage. Structural compaction should come from the project or supplier method, not a universal guess.
• Ordering to too many decimal places. The geometry may be precise, but real delivery quantities, moisture and field conditions are not. Round in the direction your supplier sells.
• Ignoring delivery constraints. Ask about truck capacity, minimum loads, access, dump location and whether the quoted amount is by scale weight or volume.

How to get the most reliable order quantity

The best estimate is not necessarily the one with the most decimals. It is the one built from good measurements and product-specific information. Before placing a large order:

• measure the finished area again;
• confirm the intended finished depth and whether it is loose or compacted;
• confirm the exact aggregate product and gradation;
• ask the supplier for its density or yards-to-tons conversion;
• ask what unit the supplier actually bills by;
• decide whether you need an order allowance for the real site conditions;
• confirm delivery minimums and truck access.

Frequently asked questions

Final note: SonoCalculator's Gravel Calculator is a quantity-planning tool. Geometry-based volume is deterministic from the measurements entered, but gravel weight and loose-to-compacted ordering quantities depend on the actual aggregate and site conditions. For a final bulk order, use your supplier's product density and the project's specified finished depth and compaction requirements.