Gravel Calculator

A gravel calculator turns three simple inputs, the plan area, the depth of the gravel layer, and the type of aggregate, into a precise order quantity in cubic metres (or cubic yards) and tonnes (or US tons). It is used by homeowners laying a new driveway, landscapers ordering pea gravel for a garden path, builders preparing a road base, and drainage contractors filling a French drain. Without it, people routinely order 20 to 30% too little (because they forget compaction) or 20% too much (because they round up too aggressively), wasting either money or a Saturday afternoon.

Gravel, crushed stone, pea gravel, river rock, decomposed granite, and sand are all sold by volume and by weight, but those two price points do not move together the way people expect. A cubic yard of crushed stone weighs about 2,700 lb; a cubic yard of pea gravel weighs about 2,500 lb; a cubic yard of sand weighs 2,800 to 3,000 lb. Converting between volume and weight requires the material's bulk density, which varies with moisture, grading, and compaction. That conversion is the most common source of ordering error, and is the reason this calculator reports volume and mass in parallel.

Where Gravel Shows Up

Gravel and crushed stone appear in almost every outdoor construction or landscaping project:

• Driveways and parking areas. A residential driveway typically uses 7.5 to 10 cm (3 to 4 inches) of compacted crushed stone (#57 or similar) over a geotextile and a 10 to 15 cm road-base layer. The decorative top layer is often pea gravel or river rock at 5 cm depth.
• French drains and perimeter drains. A perforated pipe sits in a trench backfilled with washed crushed stone or pea gravel; the open voids let groundwater in and the pipe carries it away.
• Concrete sub-base. A 10 to 15 cm layer of compacted road base or crushed stone is the standard preparation under a concrete slab. It caps the subgrade, distributes load, and prevents the slab from pumping water.
• Landscaping and garden beds. Decorative gravel, pea gravel, river rock, decomposed granite, or marble chips, at 5 to 7 cm depth suppresses weeds, conserves moisture, and finishes a bed visually.
• Garden paths and stepping-stone walkways. 5 to 8 cm of pea gravel or self-binding gravel over a compacted sub-base; the path stays level, drains well, and is easy to maintain.
• Erosion control. Coarse rip-rap (large river rock or quarry stone) lines drainage ditches, swales, and shoreline edges; it absorbs energy that flowing water would otherwise use to scour the soil.
• Pipe and utility bedding. Sand or pea gravel cushions buried pipe and conduit; its fine, rounded particles distribute load without point-loading the pipe wall.

Each of these uses wants a different gravel type and a different depth, but the calculation underneath, area times depth, multiplied by density, adjusted for compaction, is the same.

How to Use the Gravel Calculator

1. Pick Solve for in the dropdown. Most users will use the default Volume + Mass (from area & depth). Choose Depth (from area & volume) if you already know the total volume you want and need to know how deep that lands. Choose Area (from volume & depth) if you are working backwards from a delivery quantity.
2. Choose the area shape that matches the project: rectangle or square (driveway, path, patio), circle (pond, tree ring, post hole collar), or triangle (irregular patio or wedge-shaped bed).
3. Enter the dimensions in metres (metric) or feet (imperial). For a rectangle, length × width. For a circle, radius (half the diameter). For a triangle, base × perpendicular height.
4. Enter the depth in centimetres (metric) or inches (imperial). Path: 5 cm. Driveway top: 7 to 10 cm. Driveway full build-up: 20 to 30 cm.
5. Select the gravel type. The default Crushed stone (#57 / #411) is the structural choice; Pea gravel and River rock are decorative; Decomposed granite gives a firm path surface; Sand is the bedding under pavers or pipes; Road base is the compacted structural layer.
6. Set the compaction factor between 1.00 and 1.30. Loose decorative gravel: 1.00. Walked-on path: 1.10. Plate-compacted driveway: 1.20. Proctor-tested road base: 1.30. The calculator multiplies the loose volume by this factor to get the delivered mass.
7. Click Calculate. The result panel shows volume in m³, ft³, and yd³, plus mass in metric tonnes, kilograms, US tons, and pounds.

The Formulas

The calculator is built on three core relations: the geometric area, the volume, and the mass.

Volume from area and depth:

V = A × d

where V is volume in cubic metres, A is the plan area in square metres, and d is the depth in metres. Convert depth to metres first (centimetres ÷ 100; inches × 0.0254) before multiplying.

Mass from volume and density:

M = V × ρ × C

where M is mass in tonnes, ρ is the loose bulk density in tonnes per cubic metre, and C is the compaction factor (a dimensionless multiplier between 1.00 and 1.30).

Area by shape:

• Rectangle / square: A = L × W
• Circle: A = π × r²
• Triangle: A = ½ × b × h

Volume conversion factors (metric ↔ imperial):

Mass conversion factors:

Solve-for back-relations:

• Depth from area & volume: d = V / A
• Area from volume & depth: A = V / d

All conversions run inside the calculator, you can enter metric dimensions and read imperial output (or vice versa) without retyping anything.

Worked Examples

Example 1, Residential driveway (metric). A 10 m × 5 m driveway at 5 cm depth of crushed stone, no compaction.

Area = 10 × 5 = 50 m²
Volume = 50 × 0.05 = 2.5 m³
Mass (loose) = 2.5 × 1.60 t/m³ = 4.0 t

At a 1.20 compaction factor (driveway plate-compacted):

Mass = 2.5 × 1.60 × 1.20 = 4.8 t

In imperial: 2.5 m³ × 35.3147 = 88.3 ft³ = 3.27 yd³. 4.8 t × 1.10231 = 5.29 US tons.

Example 2, Circular pond edge, river rock (metric). A ring of river rock 3 m radius at 20 cm depth around a pond, lightly compacted (1.25).

Area = π × 3² = 28.27 m²
Volume = 28.27 × 0.20 = 5.65 m³
Mass (loose) = 5.65 × 1.40 = 7.92 t
Mass (compacted) = 7.92 × 1.25 = 9.90 t

The full 5.65 m³ equals 7.40 yd³ or 10.91 US tons.

Example 3, Triangular patio, sand bedding (metric). A right-triangle patio with base 6 m and height 4 m, with a 7 cm sand bedding layer, lightly walked (1.15).

Area = ½ × 6 × 4 = 12 m²
Volume = 12 × 0.07 = 0.84 m³
Mass (compacted) = 0.84 × 1.70 × 1.15 = 1.64 t

Example 4, Pea gravel path (imperial). A 50 ft² area at 4 inches depth of pea gravel, light compaction (1.10).

Depth = 4 × 0.0254 = 0.1016 m
Area = 50 / 10.7639 = 4.645 m²
Volume = 4.645 × 0.1016 = 0.472 m³ = 0.617 yd³ = 16.67 ft³
Mass (compacted) = 0.472 × 1.50 × 1.10 = 0.779 t

In US units: 0.779 t × 1.10231 = 0.858 US tons = 1,716 lb.

Example 5, Solving backwards (depth from area + volume). You have a 12 m × 8 m pad and want exactly 6 m³ of crushed stone. How deep must the gravel be?

Area = 12 × 8 = 96 m²
Depth = 6 / 96 = 0.0625 m = 6.25 cm

The calculator's Depth solve-for returns this directly, alongside the mass the same volume produces (≈ 9.6 t at 1.0 compaction, ≈ 11.5 t at 1.20).

Common Mistakes

Forgetting compaction. A neat V = A × d calculation gives the loose volume, before the material settles. A plate-compacted crushed-stone layer occupies about 15 to 25% less volume than the loose pile. Plan a compaction factor of 1.10 to 1.30 or you will run short on the second trip.

Mixing metric tonnes and US tons. A "ton" in the US is 2,000 lb (907.18 kg). A "tonne" or "metric ton" elsewhere is 1,000 kg. They differ by 10%. Always confirm which one your supplier means before placing the order.

Converting by density you don't actually have. The density tables here are typical for loose, damp material as delivered. Wet sand weighs 5 to 10% more than dry sand; a vibrated crushed-stone lift is denser than a hand-tamped one. If you have a supplier's spec sheet, use that number instead.

Ignoring slope and drainage. Gravel on a flat site turns into a puddle after the first rain. Crown the surface 2 to 3% (¼-⅜ inch per foot) so water sheds. For French drains, slope the perforated pipe at 1% minimum.

Skipping the geotextile. Without a separation fabric between the gravel and the subgrade, fines migrate up into the voids, weeds grow through, and the gravel layer gradually disappears into the mud. A £1/m² woven geotextile doubles the lifetime of any gravel surface.

Forgetting to convert depth to metres. Centimetres and inches are both common in DIY contexts. The calculator handles both unit systems internally, but if you copy a depth from one calculator into another, double-check the units, a 5 cm depth is 0.05 m, not 5 m.

Over-ordering to "be safe". The compaction factor and 5 to 10% waste allowance already give a comfortable margin. Adding another 30% on top of that doubles your delivered cost and leaves a pile of gravel in the driveway.

Frequently Asked Questions

How much gravel do I need for a driveway? A typical two-car driveway 10 m × 5 m at 5 cm depth needs 2.5 m³ of crushed stone (about 4 tonnes at 1.6 t/m³, loose). For a 10 cm compacted lift, multiply by 1.20: about 6 tonnes, or 5 m³. In US units, a 33 ft × 16 ft driveway at 2 inches deep needs about 3.3 yd³ (≈ 4.4 US tons) of crushed stone; at 4 inches compacted, about 6.6 yd³ (≈ 8.9 US tons).

How deep should gravel be? For a garden path: 5 cm (2 inches). For a residential driveway top layer: 7.5 to 10 cm (3 to 4 inches) over a compacted sub-base. For a road or heavy-vehicle driveway: 15 cm (6 inches) over a 10 to 15 cm road-base layer. For French drain backfill: at least 30 cm above and below the pipe, with a geotextile sock around the pipe itself in fine soils.

What's the difference between pea gravel and crushed stone? Pea gravel is rounded, river-worn or screened, so the particles do not interlock. It is comfortable to walk on, good for paths and decorative beds, but shifts under vehicle traffic. Crushed stone has angular faces that lock together under compaction, giving a stable surface for driveways and road bases. Use pea gravel where aesthetics and drainage matter; use crushed stone where structural strength matters.

Should I order by the ton or by the cubic yard? Both work. Ordering by volume (cubic yard or cubic metre) is easier when you know the area and depth; ordering by weight is easier when the delivery truck has a known payload (most US dump trucks are rated 10 to 15 US tons). If your supplier quotes one unit and you want the other, convert using the material's bulk density, crushed stone ≈ 1.35 US tons/yd³, pea gravel ≈ 1.26 US tons/yd³, river rock ≈ 1.18 US tons/yd³, sand ≈ 1.43 US tons/yd³, road base ≈ 1.56 US tons/yd³.

How much does a cubic yard of gravel weigh? A loose cubic yard weighs roughly 2,500 to 3,200 lb depending on material: pea gravel ≈ 2,500 lb, crushed stone ≈ 2,700 lb, river rock ≈ 2,400 lb, sand ≈ 2,800 to 3,000 lb, road base ≈ 3,100 lb. Wet gravel weighs 5 to 10% more than dry.

Do I need to compact gravel by hand? For decorative paths, no, a rake and a foot-stomp are enough. For driveways and road base, yes: rent a plate compactor (about £80-£120/day in the UK, $90-$150/day in the US). Three passes over a 5 to 7 cm lift gives a tight, well-bonded surface.

Can I lay gravel directly on soil? You can, but it will not last. The gravel migrates into the subgrade, weeds come through, and rain turns the surface into mud. Lay a woven geotextile over compacted subgrade, then a 10 cm road-base layer, then the decorative gravel. The full build-up for a residential driveway is typically 20 to 30 cm (8 to 12 inches) deep.

How much does a tonne of gravel cover? At a 5 cm depth, 1 tonne of crushed stone covers about 12.5 m² (135 ft²). At 10 cm depth, half that, about 6.25 m² (67 ft²). Pea gravel (lighter, 1.5 t/m³) covers slightly more area per tonne: about 13.3 m² at 5 cm.

References

• ASTM C29 / C29M, Standard Test Method for Bulk Density (Unit Weight) and Voids in Aggregate. ASTM International, West Conshohocken, PA.
• ASTM D698, Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort. Used to derive the Proctor density that road-base compaction targets.
• University of Georgia Cooperative Extension, Gravel and Crushed Stone for Driveways and Walkways, Landscaping Bulletin.
• University of Maryland Extension, Hardscaping: Materials for Patios and Walkways, home and garden information.
• Purdue University Extension, Driveways: Materials and Construction, agricultural and consumer-horticulture publication.