Crushed Stone Grades Explained: #2, #4, #8, #57, and #67

Crushed stone grades are classified by ASTM numbered designations that correspond to sieve analysis results, with each number defining the range of particle sizes present in that material. Knowing what each grade contains, how it behaves under load, and what it is best suited for will prevent costly material selection mistakes before your project begins.

How Crushed Stone Grades Work

Crushed stone gradation is determined by passing aggregate through a series of standardized sieves. The ASTM C33 specification defines numbered grades by specifying what percentage of the material must pass through or be retained on specific sieve sizes. An open-graded aggregate contains only a narrow range of particle sizes, leaving large voids between pieces. A well-graded aggregate spans a broad range of sizes, with smaller particles filling the voids between larger ones. Most numbered crushed stone grades are open-graded, which is why they drain freely but do not compact into a dense, stable mass the way crusher run does.

The numbered grade system does not indicate hardness, color, or rock type. A #57 stone sourced from a limestone quarry and a #57 stone sourced from a trap rock quarry are both #57 by gradation but have different densities and hardness characteristics.

Grade #1 Stone

#1 stone is the largest of the standard crushed stone grades, with a size range of approximately 2 to 4 inches. Material at this size is angular, heavy, and used primarily in large-scale drainage and erosion control applications. In residential settings, #1 stone is rarely specified, though it is sometimes used as a drainage aggregate around foundation walls or in large French drain systems where flow volume is high and clogging risk must be minimized. At this size, the aggregate is close in character to smaller rip rap, and for steep slope or streambank erosion control, true rip rap in appropriate sizes is usually the correct specification rather than #1 stone.

Grade #2 Stone

#2 stone spans approximately 1.5 to 3.5 inches, making it a large, coarse aggregate suitable for applications where maximum drainage capacity and erosion resistance are needed. Common residential uses include drainage fill behind large retaining walls, underslab drainage in areas with high groundwater, and decorative boulder-scale rock accents in landscape beds. #2 stone is too large for use as a driveway surface aggregate and too coarse for concrete mix design in most standard structural applications.

Grade #4 Stone

#4 stone covers a size range of approximately 1 to 2.5 inches, falling between the large #2 and the widely used #57. It functions well as a drainage aggregate in applications where slightly more flow capacity is needed than #57 provides, such as French drains in clay soils with high infiltration demand or drainage layers beneath sports fields and permeable pavements. #4 stone is also used as a railroad ballast size in some regions.

Grade #8 Stone

#8 stone is a fine crushed stone with a size range of approximately 3/8 inch, making it the smallest of the standard open-graded aggregates. Its small size makes it useful as a top-dressing aggregate on pathways and patios, as a fine drainage layer beneath geotextile fabric, and as an aggregate in certain concrete mixes where a smooth finish is required. #8 stone is sometimes used as a joint-filling aggregate between large flagstone pieces, though stone dust is more commonly specified for that application. Because its pieces are small, #8 stone can be displaced easily and requires good edging to stay in place as a surface material.

Grade #57 Stone

#57 stone is the most widely used numbered crushed stone grade and the one most homeowners will encounter by name. Its size range of approximately 1/2 to 1 inch, combined with its excellent drainage performance and versatility as a concrete aggregate, makes it the default specification for French drains, pipe bedding, driveway drainage layers, and coarse aggregate in ready-mix concrete. The full specification, performance characteristics, and use-case guidance for this grade are covered in our dedicated #57 stone guide.

Grade #67 Stone

#67 stone is similar to #57 in appearance and application but is slightly smaller, with a size range of approximately 3/4 inch with a tighter gradation than #57. The practical performance difference between #57 and #67 in most residential applications is minimal, and availability of one versus the other varies significantly by region. Where #57 is widely available, it is generally the preferred specification. Where a quarry offers #67 but not #57, #67 will perform similarly in drainage and bedding applications. Some state highway specifications call for #67 rather than #57, so for projects that require state DOT compliance, confirm which grade applies to your jurisdiction.

Grade #2A Stone (PennDOT Specification)

#2A is a Pennsylvania DOT specification rather than an ASTM standard grade. It is a dense-graded aggregate similar in concept to crusher run, containing a range of particle sizes from fines through approximately 1.5 inches. Like crusher run, #2A compacts well and is used as a base material under driveways, parking areas, and paved surfaces. Homeowners in Pennsylvania and surrounding states may encounter #2A as the standard base material specification at local quarries. It performs comparably to crusher run from a compaction standpoint.

#89 Stone vs #57 Stone

#89 stone is a fine open-graded aggregate with a nominal size of approximately 3/8 to 1/2 inch, smaller than #57 and larger than stone dust or fine screenings. It is used in chip seal paving, as a fine drainage layer, and occasionally as a landscape surface material. Compared to #57, #89 stone is smaller, has a lower void ratio per unit volume, and compacts slightly better, though neither grade compacts well enough for use as a structural base. For drainage applications, both grades perform well, with #57 offering marginally higher flow capacity due to larger void spaces. #89 is less commonly stocked at residential suppliers than #57.

Comparison Table

For the complete size reference covering all grades alongside specialty materials and the ASTM sieve analysis method, see our stone and gravel sizes overview. For the full crushed stone grade chart including visual references, see our crushed stone size chart.