Understanding Crushed Stone Sizes
Crushed stone is sold by number grades that describe the stone size, and picking the right grade matters more than most buyers realize. The workhorse is #57 stone — roughly 3/4-inch angular rock that drains freely and compacts into a stable surface, which is why it appears in everything from driveway toppings to French drains to concrete mixes. Crusher run (also sold as #21A, road base, or ABC) mixes angular rock with stone dust; the fines lock the mass into a near-solid mat when compacted, making it the standard foundation layer under driveways and paver patios. Smaller #8 stone suits pathways and pipe bedding, while large rip rap armors slopes and shorelines against erosion.
| Grade | Size | Density (t/yd³) | Best For |
|---|---|---|---|
| Stone dust / screenings | < 1/8" | 1.35 | Paver leveling, path topping |
| #8 stone | 3/8" | 1.45 | Paths, pipe bedding, pea-sized angular needs |
| #57 stone | 3/4" | 1.50 | Driveway surface, drainage, concrete |
| Crusher run / #21A | 3/4" + fines | 1.60 | Compacted bases and foundations |
| #3 stone | 1–2" | 1.50 | Muddy driveway repair, heavy drainage |
| Rip rap | 3–8" | 1.70 | Erosion control, embankments |
The Formula This Calculator Uses
Volume in cubic yards equals length × width × depth (all in feet) divided by 27, and tonnage equals cubic yards times the grade's density. For example, a 25 × 10 ft drainage strip at 4 inches of #57 stone is 25 × 10 × 0.333 = 83.3 cubic feet = 3.09 cubic yards × 1.5 = 4.6 tons. As always, add 5–10% for compaction and settling — angular stone compacts more than rounded pea gravel, so lean toward 10% for base work. Cross-check any quote against the coverage chart.