What Is Gravel? Types, Sizes, and How Much You Need

What Is Gravel?

Gravel is loose rock fragments, either naturally rounded by rivers and glacial movement or mechanically crushed from larger stone, sorted by size for use in construction, drainage, and landscaping. It sits between sand and larger crushed stone on the particle size scale, and it is one of the most widely used materials in paving and construction precisely because it compacts into a stable, load bearing layer while still allowing water to drain through it.

If you've ever ordered a driveway base, seen a construction site before the asphalt goes down, or filled in a low spot in your yard, you've almost certainly worked with some form of gravel already, even if nobody called it by its specific size name.

Types of Gravel Explained

Not all gravel is the same material, and the differences matter more than most people expect when it comes to how it performs.

Crushed stone is mechanically broken down from larger rock, giving it angular, jagged edges. Those rough edges are actually an advantage structurally, since angular pieces lock together tightly when compacted, which is exactly why crushed stone dominates driveway bases and structural fill.

Pea gravel is naturally rounded, typically sourced from riverbeds, and noticeably smoother underfoot than crushed stone. It looks better in landscaping and walkways but compacts far less effectively, since rounded pieces roll past each other instead of locking together, so it's a poor choice anywhere structural stability matters.

Crusher run, sometimes called quarry process or dense graded aggregate, is a blend of crushed stone in a range of sizes down to fine dust. The mix of particle sizes fills the gaps between larger pieces, producing the densest, most stable compaction of any common gravel type, which is why it's the standard choice under driveways and roads.

River rock is larger, naturally rounded stone, generally an inch or more across, used mostly for drainage channels and decorative landscaping rather than any structural application.

Gravel Sizes: What the Numbers Actually Mean

If you've ever gotten a quote that just said "#57 stone" and had no idea what that meant, you're not alone. Gravel and crushed stone sizes in the United States follow a standardized numbering system defined by ASTM International under specification D448, also adopted by state transportation departments under AASHTO M43. The system runs backward from what feels intuitive: smaller numbers mean larger stone, and larger numbers mean smaller stone.

A few sizes come up constantly in residential and driveway work. #57 stone is graded from about 1 inch down to a No. 4 sieve, roughly grape sized pieces, and is probably the single most common size ordered for driveways and drainage, since it drains well and compacts reasonably. #8 stone runs smaller, from about 3/8 inch down to a No. 8 sieve, closer to pea sized, and shows up often in concrete mixes and smaller drainage applications. #10, sometimes called stone dust or screenings, is the fine end of the scale, crushed nearly to powder, used mainly as a leveling layer or in masonry work rather than as a structural base on its own.

Knowing the actual size number, not just the word "gravel," is what gets you an exact, comparable quote from every supplier you call, since "driveway gravel" means something slightly different at every yard, but "#57 crushed stone" means the same thing everywhere in the country.

Common Uses for Gravel

Gravel's most common structural job is as a base layer, the compacted foundation that sits under asphalt, concrete, or pavers and does most of the actual work of supporting vehicle weight and managing water. Our guide to road base material covers exactly how that base layer functions and how deep it needs to be for different project types.

Beyond base work, gravel gets used as a standalone driveway surface on its own, for drainage beds and French drains, as decorative landscaping, and as backfill around underground utilities and pipe. Each use case tends to call for a different type and size, which is exactly why "what kind of gravel do I need" doesn't have one universal answer.

Figuring Tons of Gravel: How Much You Actually Need

Once you know your area and target depth, figuring tons of gravel comes down to area, depth, bulk density, and the difference between the finished compacted layer and the material delivered loose. There is no single density that is correct for every gravel product or every supplier. Gradation, moisture, and handling can change the mass to volume relationship, so supplier data should take priority over a generic conversion.

For a mixed gravel project, our gravel calculator provides editable planning assumptions and a custom density option. If you are specifically ordering crusher run, the crusher run calculator goes further by separating finished volume from planning loose order volume and adding supplier rounding, truckloads, reverse coverage, and cost. If a supplier quoted volume and you only need a unit conversion, use the cubic yards to tons calculator.

Gravel Driveway vs. Asphalt Driveway: Cost and Maintenance Compared

Gravel wins clearly on upfront cost, typically running one third to one half the price of a fully paved asphalt driveway for the same area, since there's no binder to buy and no specialized paving equipment or crew required. Our asphalt cost calculator lets you price out the asphalt side directly so you can compare a real number against your gravel estimate rather than a rough guess.

Where asphalt pulls ahead is long term maintenance. A gravel driveway needs regular regrading and periodic replenishment as stone scatters and washes away over time, along with more effort keeping it weed free and rut free. Asphalt costs more to install but, with routine sealcoating, holds a stable, low maintenance surface for fifteen to twenty years. Our driveway cost calculator guide breaks down the full asphalt side of that comparison, including realistic cost ranges by driveway size.

Frequently Asked Questions

What is gravel made of?
Gravel is loose rock fragments, either naturally rounded from rivers and glacial deposits or mechanically crushed from larger stone, sorted by size for use in construction, drainage, and landscaping.

What does gravel size #57 mean?
Number 57 is a standard size designation under ASTM D448 and AASHTO M43, describing a graded stone blend that passes a 1 inch sieve down to a No. 4 sieve. It is one of the most common sizes for driveways and drainage.

How many tons is a yard of gravel?
There is no universal tons-per-yard figure for gravel. Bulk density varies with the aggregate, gradation, moisture, and whether the measurement is loose or compacted, so use supplier data when available.

Is a gravel driveway cheaper than asphalt?
Yes, a gravel driveway typically costs significantly less upfront than asphalt, often one third to one half the price for the same area. Gravel requires more frequent maintenance over time, while asphalt costs more initially but needs less ongoing upkeep.