Quick Verdict
Crushed rock sizes in Oregon are named by the largest stone in the mix and whether the fines are left in. A "minus" product (like 3/4 minus) keeps the dust and compacts tight; a clean or open-graded product screens the fines out and drains. Bigger rock goes deep as a base or to bridge mud, and minus goes on top because it locks into a firm surface. Reading a size spec is mostly knowing what the number means and whether you want compaction or drainage. Size rarely changes the price much; the haul does.
Why Rock Size Even Matters
Rock is not just rock. The size and gradation decide whether a material compacts into a hard surface or drains water, and using the wrong size for the job is why driveways pump and drains clog. Understanding sizes lets you order the right product the first time. This is a starting-point topic; for the full materials picture, see our excavation materials and hauling guide.
How Rock Is Sized and Sieved
Crushed rock starts as quarried stone run through a crusher and then screened over sieves. The screens sort the rock by size. A product's name tells you the largest stone that passes and, often, whether the fine material is kept or removed.
- A "1.5-inch" product has stone up to about an inch and a half across.
- A "3/4 minus" has stone from 3/4-inch down to dust ("minus" means the fines are included).
- A "clean" or open-graded product has the fines screened out, leaving uniform stone.
So the number is the top size, and the "minus" or "clean" tells you about the fines.
What the Number Means
Here is how the common Oregon sizes line up and what each is for.
| Size Spec | What It Is | Typical Use |
|---|---|---|
| 1.5-inch | Larger angular stone | Deep base, mud bridging, drainage |
| 3/4 minus | 3/4-inch down to fines | Driveway surface, compacted base |
| 5/8 minus | Slightly finer minus | Pathways, tighter finish surfaces |
| 1/4 minus | Fine crushed with dust | Top dressing, smooth fine grade |
How to Read a Size Spec
When you hear a spec, break it into two questions:
- What is the top size? The number (1.5-inch, 3/4, 5/8, 1/4) tells you the largest stone.
- Are the fines in or out? "Minus" means fines are in and it compacts. "Clean" or "open-graded" means fines are out and it drains.
Answer those two and you know what the material does. A 3/4 minus compacts; a 3/4 clean drains. Same top size, opposite behavior. The broader naming and types are covered in our gravel types explained for excavation guide.
Big Rock vs. Fines: Compaction vs. Drainage
This is the core trade-off. Fines (the dust) fill the gaps between larger stones. When fines are present and you compact, the material locks up tight and forms a hard surface. When fines are absent, the voids stay open and water flows through.
- Want a firm surface? Use a minus product with fines so it compacts.
- Want water to move? Use a clean, open-graded product with no fines.
That is why a base layer often uses bigger rock for strength and drainage, and the top wearing course uses a minus that compacts into a smooth, hard surface.
Why Layers Use Different Sizes
A good gravel section is layered by size on purpose:
- Bottom: larger or open-graded rock to bridge soft ground and let water move.
- Middle/top: dense-graded minus that compacts into the driving surface.
Putting a smooth minus directly on mud lets it pump; putting big open rock on top leaves a rough, loose surface. Matching size to layer is the whole game.
A Note on Oregon Rock and Cost
Local pits set their own gradations, so the exact spec names vary by supplier. Oregon also has two common rock characters: angular basalt, which locks together and compacts well, and rounder river gravel, which rolls and does not knit as tightly. Angular minus makes the firmest driveway.
On cost, size rarely moves the price much by itself. Haul distance from the pit is the real driver. These are baseline per-yard ranges, not fixed prices.
| Driver | Baseline Range |
|---|---|
| Crushed gravel, delivered, per cu yd | $45 - $110+ per cu yd |
| Fill / pit run, delivered, per cu yd | $20 - $75+ per cu yd |
| Mobilization / delivery | $250 - $800+ flat |
These are industry baseline ranges for planning only -- actual pricing depends on site conditions, soil, access, depth, haul-off, and current market conditions. Get a site-specific quote.
Current Market Reality
Real costs often run 2 to 3 times the bare material baseline once a long quarry haul, delivery minimums to rural sites, and the depth you actually need are added in. The size you choose is a small part of the bill compared to how much you need and how far it travels.
Why Gradation Matters as Much as Size
The top size gets the name, but the gradation, the full spread of sizes in the mix, is what really decides how the material behaves. A well-graded minus has a smooth range from the top size down to dust, so the small pieces fill the gaps between the big ones and the whole thing compacts dense and tight. A gap-graded or poorly graded product, missing some middle sizes, will not pack as well no matter what the top size is.
This is why two products with the same name from different pits can perform differently. The pit's gradation, how cleanly it is sized and how much fine material it carries, affects compaction. For a driveway or base, you want a well-graded minus that locks up, not just any product labeled with the right top size. A contractor who knows the local pits knows which products actually compact.
Buying the Right Amount, Not Just the Right Size
Once you know the size you need, the other half of ordering is the quantity, and getting that wrong costs more than getting the size wrong. Order too little and you pay a second delivery and minimum; order too much and you have a pile you did not need. The amount comes from the area, the depth, and an overage factor for compaction loss.
For most projects, you calculate the cubic yards from length times width times depth, then add roughly 10 to 15 percent because the rock loses depth when it is spread and compacted. Crushed rock is heavy, so if your supplier sells by the ton you convert yards to tons before ordering. Getting both the size and the amount right is what turns a materials order into a finished surface without a second trip to the pit.
The Bottom Line
Crushed rock size is just the top stone plus whether the fines are in. Minus compacts, clean drains, big rock bridges, fine rock finishes. Pick the size by the job each layer does and you will order right the first time. Our excavation services crew specs and places the right gradation for your project. To plan a materials order, request a free estimate.