Last updated: September 30, 2025
Measure your area, choose a depth and material, and use our calculator to convert the volume into cubic metres/yards and tonnes using density ranges. Adjust for compaction and waste, then convert to bags or truckloads. Results are estimates – check with your supplier because densities vary by source and moisture.
Calculating stone requirements for a job is really not that simple: one must look into the weight of aggregates concerning particle size, shape, moisture, and gradation. Stone suppliers sell their product by volume (cubic yards or cubic metres) or weight (tons, tonnes, or kilograms). They frequently round off quantities to the nearest truck or bulk bag. This article discusses the theory about stone calculators and choosing materials and grades. It also provides information about depths, layering, and best practices for placing orders. All estimates returned by the Calculator are estimates-the world is messy, so always confirm with your supplier or engineer on the actual dimensions and densities. The guidelines here reference general standards (AASHTO M 43/M 147, ASTM C33/C136/C295, BS EN 13242).
Estimate the volume and weight of stone, gravel or aggregate for your project.
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Help & FAQs
Why do I need a waste allowance?
Stone and gravel settle and compact. Adding a small waste percentage (5–10 %) helps ensure you order enough material.
How deep should I lay aggregate?
For 10 mm aggregate use 30–40 mm depth; on driveways use about 50 mm. For 20 mm aggregate use 40–50 mm depth, increasing to 50–60 mm on driveways.
How do units convert?
1 inch = 25.4 mm. 1 cubic yard = 27 cubic feet and 46 656 cubic inches. 1 cubic meter = 1.30795 cubic yards.
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How the calculator works
A simple volume formula is at the heart of every stone calculator: Volume = Length × Width × Depth. For rectangular areas such as patios, footpaths, and driveways, multiply the length, width, and thickness in consistent units to get cubic feet; divide by 27 to convert to cubic yards. For example, a patio measuring 20 ft by 12 ft with a depth of 4 inches (0.333 ft) has a volume of 79.9 ft³ (20 × 12 × 0.333) or 2.96 yd³ (79.9 ÷ 27).
For circular areas, measure the diameter, divide by 2 to obtain the radius, and compute area = π × r². Multiply by the Depth to get volume. A circular flower bed with a diameter of 3 m and a depth of 75 mm (0.075 m) has a volume of π × (1.5 m)² × 0.075 m ≈ 0.53 m³. Converting to yards (0.53 × 1.30795) yields 0.69 yd³. Some tools treat trenches as long, thin rectangles; for borders, multiply the border length by the strip width and Depth.
Irregular shapes require approximating the area. Our Calculator lets users draw a polygon or enter a series of lengths and widths; the tool divides the shape into rectangles and sums their areas. When manually measuring irregular areas, divide the space into smaller rectangles or triangles, calculate each location, and add them together. Always use the same unit for all dimensions before multiplying.
Unit conversions
Stone projects use both metric and imperial units. To make life easier, our Calculator performs all conversions automatically. Key conversions include:
- Length: 1 in = 25.4 mm; 1 ft = 12 in = 0.3048 m; 1 yd = 3 ft = 0.9144 m. For metric dimensions, 1 cm = 0.01 m and 1 mm = 0.001 m.
- Volume: 1 m³ = 35.3147 ft³ and 1.30795 yd³. Conversely, 1 ft³ = 0.0283 m³ and 1 yd³ = 0.7646 m³.
- Weight: 1 metric tonne (t) = 1,000 kg; 1 US ton (short ton) = 2,000 lb = 907.185 kg. Therefore, to convert kilograms to US tons, divide by 907.185; to convert kilograms to metric tonnes, divide by 1,000.
In our implementation, we use banker’s rounding (round half to even) to avoid systematic upward bias when displaying volumes and masses to two or three decimal places.
Density, grades and tonnage
Volume is only half the story: you need weight to order stone by ton or tonne. Weight is calculated as Mass = Volume × Density. Density depends on the rock type, gradation, and moisture content. Typical dry densities for common aggregates fall between 1,400 kg/m³ and 1,800 kg/m³. The Calculator notes that crushed stone or gravel smaller than 2″ usually weighs 1.4 – 1.7 tons per cubic yard. Larger rocks and riprap weigh slightly more (1.5 – 2.0 t/yd³), while lightweight lava rock can be as low as 0.65 t/yd³.
For more precise estimates, densities should be linked to specific grades. The American Association of State Highway and Transportation Officials (AASHTO) standard M 43 and the related ASTM D448 define gravel and crushed stone grades based on sieve sizes. Grade numbers correspond to the number of openings per inch; for example, #57 aggregate passes a ¾″ (19 mm) sieve with specific percentages passing smaller sieves. In Europe, BS EN 13242 uses a geometric progression of sieve sizes with a ratio of about 1.25.
Below is a simplified density table for common aggregates. Values are mid‑range estimates; always check supplier data.
| Grade/Material | Size range | Typical dry density (kg/m³) | Uses |
|---|---|---|---|
| #3 (coarse) | 12 – 50 mm | 1 450 – 1 650 | Road bases, stabilization, drainage |
| #8 | 9.5 – 12.5 mm | 1 550 – 1 700 | Landscaping, walkways, drainage |
| #10 screenings | < 4.75 mm | 1 450 – 1 600 | Base layer for pavers, pathways |
| #57 | ~19 mm | 1 500 – 1 700 | Driveways, concrete mixes, French drains |
| #411/21 (crusher run) | 19 mm down to fines | 1 650 – 1 750 | Dense‑grade aggregate for bases |
| Pea gravel | 4 – 10 mm | 1 550 – 1 650 | Decorative beds, pathways |
| MOT Type 1 (UK) | 40 mm down to fines | 1 700 – 1 800 | Road sub‑base |
| Riprap Class B | 150 – 300 mm | 1 700 – 2 000 | Erosion control, slopes |
| Gabion stone | 75 – 150 mm | 1 600 – 1 800 | Gabion baskets, retaining walls |
When converting cubic yards to weight, multiply by density and apply a waste factor. For example, 5 yd³ of #57 stone at 1.6 t/yd³ requires 8 t; adding a 10 % waste allowance means ordering 8.8 t.
Selecting material & grade
Choosing the right aggregate depends on the application. Gravel is a naturally eroded rock with rounded edges; crushed stone is mechanically produced and has angular faces, offering better interlock. #57 or MOT Type 1 provides a stable base for driveways and concrete mixes. Due to its smooth texture, Pea gravel suits decorative beds and play areas. Larger riprap stones are used for erosion control along slopes and shorelines. The AASHTO/ASTM grades table above helps users match their needed size.
For UK readers, MOT Type 1 is a graded granular sub‑base material containing crushed rock, recycled aggregate, and fines conforming to BS EN 13242. Single‑size 20 mm or 40 mm gravel is commonly used for drainage and soakaway projects. Our Calculator allows switching between US and metric grades and densities.
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Determining depths & layers
Multi‑layer build‑ups distribute loads and prevent rutting. A typical driveway might comprise:
- Sub‑grade preparation: Remove topsoil, level the area, and compact the native soil. Lay a geotextile fabric to prevent fines from migrating.
- Sub‑base layer: 4–6 inches of graded crushed stone (#3 or MOT Type 1) compacted in lifts.
- Base layer: 2–4 inches of #57 stone or similar, compacted.
- Bedding/levelling layer: 1–2 inches of screenings or sand for pavers.
- Decorative/top layer: 2–3 inches of pea gravel or decorative aggregate.
Our Calculator lets users add layers with different thicknesses and densities. It sums the volumes and weights and presents a consolidated bill of materials.
Waste allowance & real‑world factors
Stone settles and compacts under traffic and weather. Fines fill voids, and rounded aggregates can “pack down” more than angular ones. Moisture content adds weight; wet sand weighs 20 % more than dry sand. To avoid shortfalls, add a waste allowance. Our tool defaults to 10 %, but you can set any value between 0 % and 15 %. Use the higher end for loose or rounded materials (pea gravel, river rock) and complex shapes. For paved surfaces where compaction is critical, factor in compaction ratios (e.g., a 4 in thick loose layer may compact to 3.5 in). Always verify with your supplier – they may deliver in increments (e.g., 0.5 m³ or 0.25 yd³ loads) and recommend ordering a round number.
Moisture, voids & compaction
Aggregates contain voids between particles. The void ratio depends on gradation and shape. Well‑graded mixes (a wide range of sizes) fill voids better than single‑size gravels, resulting in higher densities and fewer voids. Moisture lubricates particles during compaction, allowing a denser pack and increasing weight. For planning, use dry densities and add a safety margin. When measuring weight on site, note whether the supplier sells by dry weight or “wet” ton—some quarries adjust for moisture.
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Using the stone calculator (step‑by‑step)
- Select shape or free‑form: Choose a rectangle/slab, circle, border/trench, or free‑form area. For free‑form, draw the outline or enter lengths and widths for each section.
- Enter dimensions: Input length, width, and Depth for rectangles/trenches; diameter and Depth for circles. Use the unit dropdown to pick ft, yd, m, cm, mm, or in. For layers, repeat this process per layer.
- Choose material & density: Pick a material (crushed stone, gravel, pea gravel, limestone, granite, riprap, etc.). The density field pre‑loads a typical value but can be edited. Advanced mode unlocks custom densities and adds a density chart referencing AASHTO/ASTM grades.
- Set waste allowance: Adjust the slider to 0 % and 15 %. Tooltips explain how compaction and irregular shapes affect waste.
- Review results: The Calculator displays volume in cubic metres, cubic feet, and cubic yards (rounded to three decimals) and weight in kilograms, tonnes, and US tons (rounded to two decimals). It also lists the number of standard bags (20–25 kg/40–50 lb), bulk bags (0.5–0.85 m³), and truckloads (specify truck capacity). Each layer’s totals and a combined total are shown.
- Export and share: Click “Print Summary” to generate a PDF; “Download CSV” to save a spreadsheet; or “Copy Summary” to copy results. A shareable link with pre‑filled inputs can be generated and sent to suppliers or colleagues.
Converting results
The Calculator performs mass conversions automatically, but understanding the math helps verify results. To convert cubic metres to kilograms, multiply by density (kg/m³). To convert to metric tonnes, divide kilograms by 1,000. To convert to US tons, divide kilograms by 907.185. For example, 1 m³ of #57 stone (density ≈ 1,600 kg/m³) weighs 1,600 kg or 1.6 t; in US tons, this is 1.6 t × 1.10231 ≈ 1.76 short tons.
Bag conversions depend on bag size. A 25 kg bag equals 0.025 t; dividing the total tonnage by 0.025 yields the number of bags. Bulk bags typically hold 0.5 m³ or about 800 kg; trucks may carry 10–20 t depending on vehicle size and local regulations. Always confirm bag and truck capacities with your supplier.
Best practices for ordering & installation
Accurate measurements and preparation reduce waste and ensure a successful installation:
- Measure multiple points: The ground isn’t perfectly level. Measure length, width, and Depth in at least three places and use the average.
- Prepare sub‑grade: Remove organic matter, large stones, and topsoil. If the soil is soft or clayey, excavate deeper and replace it with compacted gravel. Install geotextile fabric to separate soil from aggregate.
- Contain the edges: Use timber, metal, or plastic edging to hold gravel in place. Install kerbs or pavers for driveways and paths.
- Provide drainage: Slope the surface away from structures (1 % minimum) to prevent puddling. Use perforated pipes wrapped in geotextile and backfill with clean, coarse aggregate for drainage trenches.
- Compact in lifts: Place gravel in layers no thicker than 4 inches (100 mm) and compact with a plate compactor. Add water if necessary to achieve optimum moisture.
- Order extra for settlement: Even with compaction and waste allowance, gravel may settle over time. Keep a small reserve for future top‑ups.
Frequently Asked Questions (FAQs)
“Stone” is a broad term for aggregate materials used in construction. Gravel refers to naturally eroded, rounded rock fragments. Crushed stone is produced by mechanically breaking rock and has angular edges; it provides better interlock and load‑bearing capacity. Many suppliers group crushed stone and gravel together.
Multiply the volume in cubic yards by the material’s density in tons per cubic yard. Crushed stone smaller than 2″ typically weighs 1.4 – 1.7 t/yd³; riprap and large stones may weigh up to 2 t/yd³. For example, 5 yd³ of crushed stone at 1.6 t/yd³ equals 8 t.
Depth depends on use. Calculator.net notes that 2–4 inches (50–100 mm) is a workable baseline for many projects. Light footpaths may require 2 inches; driveways and parking areas need 4 – 6 inches of compacted base plus a 2 – 3 inch top layer.
Yes. Settlement, compaction and irregular shapes can consume extra material. A 5 – 15 % waste allowance covers cut‑offs and compaction. Rounded aggregates like pea gravel settle more than angular crushed stone.
In the AASHTO/ASTM system, #57 aggregate is a nominal ¾ inch (19 mm) stone with specified gradation percentages. It’s the most common aggregate for driveways, concrete mixes and French drains.
Yes. Dense‑graded mixes (e.g., #411 or crusher run) combine coarse and fine particles to create a stable, compactable base. For drainage or decorative use, single‑size gravel may be preferable. Always follow local specifications for sub‑base materials.
A US (short) ton equals 2 000 lb (907.185 kg). A metric tonne equals 1 000 kg (2 204.62 lb). Our calculator displays both and uses conversions to ensure clarity.
Divide the tonnage by the bag size. For example, 1 t = 1 000 kg. Using 25 kg bags, you need 40 bags per tonne; using 50 lb (22.7 kg) bags, you need about 44 bags per US ton.
The free‑form mode lets you draw polygons or input multiple sections. The tool calculates each section’s volume and sums them. For very complex shapes, divide the area into simple shapes and enter them separately.
Results are based on loose depth. For compacted layers, specify the compacted thickness and use the waste allowance slider to cover additional material needed for compaction. Always compact in layers and check manufacturer guidance.
