Gravel Types and Sizes: #57, Pea Gravel, Crusher Run and How Deep to Lay Them
Walk into a stone yard and you will hear numbers and nicknames: #57, #3, #411, pea gravel, crusher run, quarry process. Choosing the wrong one is the most common reason a gravel project fails. Rounded stone rolls underfoot, clean stone without fines never locks together, and a dense base without drainage stays wet.
This guide explains the common US gravel products, what they are good for, and how deep to lay them.
How gravel numbers work
In the US, many crushed-stone products are named by size numbers based on ASTM D448, a standard that groups aggregate by sieve size. The key thing to remember: the higher the number, the smaller the stone. #3 is much larger than #57, and #57 is larger than #8.
“Clean” stone means the fines (dust and small particles) have been washed or screened out. Clean stone drains freely. Stone “with fines” or “dense-graded” contains a range of sizes down to dust, so it compacts into a hard layer.
Exact gradations and local names vary between quarries and state DOT specifications, so always check the supplier’s product sheet.
The common products
| Product | Typical size | Shape / fines | Best for |
|---|---|---|---|
| #3 stone | about 1–2 in (25–50 mm) | Angular, clean | Bottom layer of driveways on soft ground, drainage |
| #57 stone | about ½–1 in (13–25 mm) | Angular, clean | Driveway middle/top layer, drainage behind walls, French drains, under pavers when specified |
| #8 stone | about ⅜ in (10 mm) | Angular, clean | Top dressing, bedding for some pipes and pavers |
| Pea gravel | about ¼–⅜ in (6–10 mm) | Rounded, clean | Paths, play areas, between stepping stones, decorative beds |
| Crusher run (also dense-graded aggregate, road base, #411, quarry process) | ¾ in or 1½ in down to dust | Angular, with fines | Compacted base under driveways, patios, sheds; driveway top surface |
| Stone dust / screenings | ¼ in down to dust | Fines | Leveling layer for flagstone, some paver installs |
| River rock | about 1–3 in (25–75 mm) | Rounded, clean | Decorative beds, dry creek beds, downspout splash areas |
Choosing by job
Driveways
Use angular stone. The flat, fractured faces interlock under load; rounded stone acts like ball bearings. A common build is larger stone at the bottom (#3 or a 1½ in crusher run) and a finer, firmer surface on top (crusher run or #57). Our driveway gravel guide works through the quantities.
Patio and paver bases
Pavers and patio stones need a compacted, dense-graded base, typically ¾ in crusher run or the base product your paver manufacturer specifies. Compact it in lifts with a plate compactor. The bedding layer on top is usually about 1 in of concrete sand or a fine clean chip, depending on the installation method the manufacturer specifies.
Walkways and garden paths
Pea gravel feels good underfoot but migrates; it needs solid edging. Crushed stone with fines makes a firmer path that is easier to push a wheelbarrow or stroller over.
Drainage
French drains, dry wells, and the backfill behind retaining walls need clean stone, usually #57, so water can move through the gaps. Never use crusher run for drainage; the fines fill the voids.
How deep to lay each layer
| Application | Base layer | Top layer | Total |
|---|---|---|---|
| Garden path (foot traffic) | 2–3 in crusher run (optional on firm soil) | 2 in pea gravel or crushed stone | 2–4 in (5–10 cm) |
| Patio / paver base (foot traffic) | 4–6 in compacted crusher run | ~1 in bedding layer | 5–7 in (13–18 cm) |
| Shed pad | 4–6 in crusher run or #57 | — | 4–6 in (10–15 cm) |
| Driveway on firm soil | 4 in crusher run or #3 | 2–4 in crusher run or #57 | 6–8 in (15–20 cm) |
| Driveway on soft soil | 4–6 in #3 | 4 in #57 + 2 in crusher run | 10–12 in (25–30 cm) |
| Decorative bed | — | 2–3 in pea gravel or river rock | 2–3 in (5–8 cm) |
Compact dense-graded base in lifts of about 2–4 in. A single 6 in lift is hard to compact all the way through with a typical rental plate compactor.
Worked example: a 12 × 16 ft paver patio base
Area: 12 × 16 = 192 ft² (3.66 m × 4.88 m ≈ 17.8 m²).
Base: 4 in of compacted crusher run. 192 × 4 ÷ 12 ÷ 27 = 2.37 yd³. Crusher run compacts noticeably, so add about 15%: 2.73 yd³. At 1.4 tons per cubic yard that is about 3.8 tons (about 2.1 m³, or 3.5 metric tonnes).
Bedding: 1 in of concrete sand. 192 × 1 ÷ 12 ÷ 27 = 0.59 yd³. Round to 0.75 yd³ or the supplier’s smallest increment.
If you also extend the base 6 in beyond each edge of the patio (a common practice so the edge restraint sits on compacted stone), the area becomes 13 × 17 = 221 ft², and the base rises to about 3.1 yd³ with the compaction allowance.
Common mistakes
- Using pea gravel as a base. It never compacts. Put it on top of a firm base, never under pavers or slabs.
- Using crusher run where water needs to drain. It is designed to pack tight and shed water, not let it through.
- Assuming #57 means the same everywhere. Gradations and local product names differ. Ask for the spec sheet if the job depends on it.
- Laying it all in one lift. Thick lifts compact on top and stay loose underneath, which leads to settling later.
- Forgetting edging. Loose stone spreads. Steel, aluminum, plastic, or stone edging keeps paths and beds at their designed depth.
Get the quantity
Once you know the product and depth, the gravel calculator turns your dimensions into cubic yards, tons and cubic metres. Run it once for each layer.
FAQ
Is #57 stone the same as pea gravel?
No. #57 is angular crushed stone roughly ½–1 in in size. Pea gravel is smaller and rounded by water. #57 interlocks and holds a shape; pea gravel shifts.
What is the difference between crusher run and #57?
Crusher run contains fines down to dust, so it compacts into a hard, fairly water-resistant layer. #57 is clean stone with no fines, so it drains well but stays loose.
How deep should gravel be for a walkway?
For foot traffic, about 2 in of top stone over firm ground is usually enough. On soft soil, add 2–3 in of compacted crusher run underneath.
Do different gravels weigh the same?
Not exactly. Most crushed stones and gravels fall roughly between 1.3 and 1.5 tons per cubic yard. Dense-graded material with fines tends to be heavier per cubic yard than clean stone. Use your supplier’s figure when ordering by the ton.