Stone and Gravel Sizes: Complete Reference Guide
Stone and gravel sizes are classified by standardized sieve analysis under the ASTM C33 specification, with each numbered grade defining the particle size range present in that material and, by extension, how it will perform in drainage, compaction, and structural applications. This reference covers every common grade from the finest screenings through large rip rap, explains how the sizing system works, and guides you to the right material for the most common residential and light commercial applications.
How Gravel and Stone Sizes Are Measured
Gravel and crushed stone sizes are determined by sieve analysis, a process in which a sample of aggregate is passed through a series of standardized wire mesh sieves with progressively smaller openings. The ASTM C33 specification defines the sieve sizes and the percentage of material that must pass through or be retained on each sieve for a given numbered grade. The result is a gradation curve that tells engineers and contractors exactly what range of particle sizes is present in a given material.
The nominal size of a graded stone refers to the approximate size of the largest pieces present. The actual size range within that grade extends from smaller than the nominal size down to the minimum size retained by the finest required sieve. When a supplier says they stock “#57 stone,” that nominal size designation means the material conforms to the ASTM C33 gradation for #57 aggregate, with pieces predominantly in the 1/2 to 1 inch range.
Open-graded aggregates contain only a narrow range of particle sizes, leaving large void spaces between pieces. These voids allow water to drain freely, which is why open-graded materials like #57 stone and pea gravel are used for drainage applications. Well-graded aggregates span a broad range of particle sizes, with smaller particles filling the voids between larger ones, producing a dense, cohesive mass when compacted. Crusher run is a well-graded aggregate and is used where compaction and stability are the priority rather than drainage.
How Gravel Size Is Measured in Practice
In practice, the ASTM sieve analysis is performed at the quarry on batches of material as quality control. Homeowners and contractors do not typically perform sieve analysis themselves, but understanding the nominal size designation and how it translates to what you see in the product is useful. A handful of #57 stone should contain pieces that are clearly larger than a pea and clearly smaller than a golf ball, with no fine material or dust. A handful of crusher run should contain everything from coarse sand and fines through to the maximum stone size.
If you are unsure about a material’s gradation before ordering, ask your supplier for the gradation certificate or the product specification sheet. Legitimate aggregate suppliers will have these documents available for any material they stock.
Complete Stone and Gravel Size Reference Table
| Material | Nominal Size | Gradation Type | Drains Freely | Compacts for Base | Primary Uses |
|---|---|---|---|---|---|
| Stone Dust / Screenings | Under 1/4 inch | Dense, fine | Limited | Yes | Paver bedding, pathway surfacing, joint fill |
| #10 Stone | 1/8 inch | Open | Yes | Minimal | Fine drainage, specialty concrete |
| #8 Stone | 3/8 inch | Open | Yes | Minimal | Pathways, fine drainage, chip seal |
| #89 Stone | 3/8 – 1/2 inch | Open | Yes | Minimal | Chip seal, fine drainage |
| Pea Gravel | 1/4 – 1/2 inch | Open, rounded | Yes | No | Patios, paths, pipe bedding, aquaria |
| #67 Stone | 3/4 inch | Open | Yes | No | French drains, pipe bedding |
| #57 Stone | 1/2 – 1 inch | Open | Yes | No | French drains, concrete, driveway drainage |
| Crusher Run | Fines to 1.5 inch | Well-graded | Limited | Yes | Driveway base, subbase, compacted surface |
| #4 Stone | 1 – 2.5 inches | Open | Yes | No | Drainage layers, sports field drainage |
| #2 Stone | 1.5 – 3.5 inches | Open | Yes | No | Large drainage, retaining wall backfill |
| #1 Stone | 2 – 4 inches | Open | Yes | No | Large drainage, erosion control |
| Rip Rap | 4 – 24+ inches | Angular, large | Yes | No | Slope protection, streambank, pond edge |
Which Stone Size Should You Use?
The right stone size depends on the specific function the material needs to perform. The four most common residential applications each have a clear material match.
Driveway Base
Driveway base layers require a well-graded aggregate that compacts to a dense, stable mass. Crusher run, also called crusher fines, processed gravel, or road base depending on the region, is the standard material. It compacts to a hard surface that resists displacement under vehicle loads. A 4-inch compacted layer of crusher run over a stable subgrade is the foundation for most residential driveways. For the full driveway gravel selection framework, see our best driveway gravel guide.
French Drain and Subsurface Drainage
French drains and perimeter drainage systems require an open-graded aggregate that allows water to move freely through the void spaces. #57 stone is the standard specification for residential French drain aggregate, placed around a perforated drain pipe and wrapped in geotextile filter fabric. Its combination of good drainage performance, availability, and moderate cost makes it the default choice. The full specification and installation context for #57 stone is in our #57 stone guide.
Concrete Mix
Concrete requires a coarse aggregate that bonds well with cement paste and provides structural strength in the hardened mix. #57 stone is the most common coarse aggregate in standard structural concrete, meeting the ASTM C33 specification that most concrete mix designs reference. Ready-mix concrete plants use #57 or a comparable material unless the project specification calls for a different aggregate.
Patio Base Layer
Patio base layers require a compactable material for the structural sub-base and a fine, level material for the screeded bedding layer beneath pavers or flagstone. The sub-base is typically crusher run compacted to a depth of 4 to 6 inches. The bedding layer is coarse concrete sand or stone dust at 1 inch depth. The full base material specification for patio installation, including how base depth varies by material type and climate, is in our best base material for a patio guide.
Erosion Control and Slope Protection
Slopes and streambanks subject to erosion from concentrated runoff need a large, angular material that resists displacement by water flow. Rip rap sized appropriately for the anticipated water velocity is the standard erosion control material for these applications. For small residential drainage swales and low-gradient slopes, Class I rip rap at approximately 6-inch median size is typically adequate. The full sizing and installation guide for rip rap is in our rip rap guide.
Specialty Materials Not in the ASTM Numbered System
Several commonly used landscape and construction materials do not carry ASTM numbered grade designations but are widely available from aggregate suppliers.
Decomposed granite is a naturally weathered material with a sandy-gravelly texture, used primarily as a pathway and driveway surface in dry climates. It is not an ASTM-graded material and its particle size distribution varies by source. Full coverage of decomposed granite, including drainage performance and how to stabilize it, is in our decomposed granite guide.
Trap rock is not a size designation but a rock type classification applied to dense, dark igneous rocks including basalt, diabase, and gabbro. Trap rock is crushed to standard ASTM numbered grades but has different physical properties from limestone aggregate of the same gradation, particularly in hardness and density. The performance differences and where trap rock is available are covered in our trap rock guide.
Stone dust, also called screenings or quarry dust, is the fine residue from the stone crushing process. It falls below the particle size range of the smallest ASTM numbered grades and compacts to a very dense mass, making it useful as a bedding layer and pathway surface but unsuitable for drainage applications. The full comparison with sand and how to use stone dust for paver bedding is in our stone dust guide.
The Full Crushed Stone Grade Reference
For a detailed, visual grade-by-grade reference including nominal sizes, sieve percentages, and photographic examples, see our crushed stone size chart. For the specific numbered grades in detail, including the #2, #4, #8, #67, and #2A specifications side by side, see our crushed stone grades guide.