Crushed stone and gravel are sold by size number, and the number tells you the range of stone sizes in the load. #57 stone, the most common, runs from about 1 in down to 3/16 in; #8 is 3/8 in and smaller. The numbers come from the standard coarse aggregate sizes used by every state highway department, so a quarry in Ohio and one in Georgia mean the same thing by them. This guide lists the standard sizes, what each is used for and how dense-graded base differs from clean stone. For cubic yards and tons, use the gravel calculator.
Gravel size chart by number
| Size number | Largest stone (nominal) | Smallest stone (nominal) | Typical uses |
|---|---|---|---|
| No. 1 | 3-1/2 in | 1-1/2 in | Large riprap-like stone for erosion control and heavy base |
| No. 2 | 2-1/2 in | 1-1/2 in | Ballast, large drainage |
| No. 3 | 2 in | 1 in | Base for driveways over soft ground, culvert drainage |
| No. 4 | 1-1/2 in | 3/4 in | Drainage, base course |
| No. 5 | 1 in | 1/2 in | Drainage and concrete aggregate |
| No. 57 | 1 in | No. 4 (4.75 mm) | The all-purpose clean stone: driveway surface, drainage behind walls, under slabs and pavers, concrete aggregate |
| No. 6 | 3/4 in | 3/8 in | Drainage, concrete aggregate |
| No. 67 | 3/4 in | No. 4 (4.75 mm) | Concrete and asphalt aggregate, walkways, pipe bedding |
| No. 7 | 1/2 in | No. 4 (4.75 mm) | Smaller clean stone for walks and bedding |
| No. 8 | 3/8 in | No. 8 (2.36 mm) | Pea-gravel-sized crushed chips, paver joints, chip seal |
| No. 89 | 3/8 in | No. 16 (1.18 mm) | Fine chips, paver joints and bedding |
| No. 9 | No. 4 (4.75 mm) | No. 16 (1.18 mm) | Coarse sand-sized chips |
| No. 10 | No. 4 (4.75 mm) | fines (dust) | Screenings / stone dust: paver and flagstone base leveling |
Two patterns are worth knowing. A single-digit size (No. 4, No. 6) is a narrow, one-size stone. A two-digit size combines two single sizes: No. 57 is No. 5 and No. 6 blended down to No. 4, and No. 67 is No. 6 plus No. 7. The more sizes in the blend, the better it packs. Sieve numbers are the openings in a standard sieve:
| Sieve | Opening | In inches |
|---|---|---|
| No. 4 | 4.75 mm | 0.187 in |
| No. 8 | 2.36 mm | 0.093 in |
| No. 16 | 1.18 mm | 0.046 in |
Clean stone versus dense-graded base
All the numbered sizes are clean: washed or screened so there are few fines. Clean stone drains freely and does not pack hard, which is what you want behind a retaining wall, around a footing drain or under a slab. It is a poor driveway base on its own, because the stones roll under tyres.
Dense-graded aggregate, sold as crusher run, crushed aggregate base, road base, DGA or (in some states) by a DOT item number, contains every size from about 1-1/2 in down to dust. Compacted in layers, the fines lock the larger stones together into a firm base. The usual driveway build-up is a compacted layer of dense-graded base, optionally over a layer of larger stone on soft ground, topped with a few inches of clean #57 or a smaller decorative stone.
Which size for which job
- Driveway base: dense-graded base (crusher run), compacted in 3 to 4 in lifts; No. 3 or No. 2 stone first where the ground is soft.
- Driveway surface: No. 57 is the common choice; smaller stone (No. 8) looks neater but scatters more.
- Drainage (French drains, behind walls, around foundation drains): No. 57, wrapped in filter fabric where soil could wash in.
- Under concrete slabs: a compacted base of clean stone or dense-graded base; the IRC calls for 4 in of graded sand, gravel or crushed stone under house floors in most soils (R506.2.2). See our concrete slab thickness guide.
- Pavers and patios: compacted dense-graded base, then a 1 in bedding layer of concrete sand or No. 8/89 chips; screenings (No. 10) are used under flagstone.
- Pea gravel: naturally rounded river gravel about 3/8 in, used for paths and play areas; it is not a numbered crushed size and does not compact.
Weight and ordering
Gravel is sold by the ton or by the cubic yard. Our gravel calculator uses about 105 lb per cu ft for dry gravel, 125 lb for wet, and 1.8 tons per cubic yard for compacted crushed stone base (a factor used by the Illinois DOT), which means one cubic yard of loose dry stone is about 1.4 tons. Clean stone and dense-graded base of the same rock weigh differently because the base packs tighter. Ask your supplier for their tons-per-yard figure, especially for compacted base, and order 5 to 10% extra for uneven ground.
Worked example: gravel driveway
A 12 x 60 ft driveway with 4 in of compacted dense-graded base and 2 in of #57 on top: base = 720 sq ft × 4 ÷ 12 = 240 cu ft = 8.9 cu yd, about 16 tons at 1.8 t/yd³ compacted; surface = 720 × 2 ÷ 12 = 120 cu ft = 4.4 cu yd, about 6.3 tons at 105 lb/cu ft. The gravel calculator does the same arithmetic for any size.
Frequently asked questions
What size is #57 gravel?
About 1 in down to 3/16 in (the No. 4 sieve, 4.75 mm). It is the standard clean crushed stone for drainage and driveway surfaces.
What size gravel is best for a driveway?
A compacted base of dense-graded aggregate (crusher run), with a 2 to 3 in surface of #57 or similar clean stone. On soft ground, start with a layer of larger stone such as No. 3.
What is the difference between #57 and #67 stone?
#57 runs from 1 in to 3/16 in; #67 from 3/4 in to 3/16 in, so it is a little smaller and is often used as concrete and asphalt aggregate and for walkways.
What does the number on gravel mean?
It is a standard aggregate size number (ASTM D448 / AASHTO M 43). Lower numbers are larger stone; two-digit numbers are blends of two sizes.
Sources
- ASTM D448 / AASHTO M 43, standard sizes of coarse aggregate: size numbers and nominal size ranges as reproduced in state DOT standard specifications (values summarised, gradation table not reproduced).
- ASTM E11, test sieves: sieve openings No. 4 (4.75 mm), No. 8 (2.36 mm), No. 16 (1.18 mm).
- Densities: the values used by our gravel calculator (dry gravel 105 lb/cu ft, wet 125 lb/cu ft; compacted crushed stone 1.8 tons per cubic yard as used by the Illinois DOT).
- International Code Council, 2021 IRC Section R506.2.2 (base under concrete floors), paraphrased.
Last reviewed: 24 October 2026. Numbers in the tables are our arithmetic from the sources listed; code sections are summarised, not quoted. How we check our work: methodology and corrections. Spotted an error? Please let us know.