Are you planning to order gravel or crushed stone for a shed base, under a deck, driveway, patio, garden path, or drainage around the house? If you are, it’s important to select the best type and size for your project. There are so many different types and sizes that selecting the correct gravel sizes can be confusing. Don’t worry, we’re here to help!
Gravel is often used to mean crushed stone but is actually a naturally occurring water-shaped rock. Its surfaces and edges have been smooth and rounded by water moving it against other rock material and waterborne debris. Crushed stone is a mechanically broken rock with rough edges and surfaces. Both gravel and crushed stone are sifted through heavy-duty screens that separate them into different sizes or grades.
In this guide, we’ll discuss the differences between gravel and crushed stone, identify the types of gravel and provide a convenient size chart. We’ll identify the types and grades of crushed stone and the differences between washed and unwashed gravel. Plus, we’ll explain how to choose the right gravel and type for your project and even provide a handy reference table to help you out. Our aim is to provide you with the information to make the best choice for your project.
Gravel vs Crushed Stones
In many areas, the term gravel is synonymous with crushed stone and means any rock material 1/8” to 4” in size and may be naturally occurring or man-made. They are commonly used for walkways, roadways, drainage, and as an aggregate in concrete. However, while gravel and crushed stone may have similar uses, they are not the same. So, it’s best to know the difference and ask for exactly what you want.
Gravel is a product of nature and typically has smooth rounded edges and is often egg, pancake, or marble-shaped. It has been shaped, sized, and smoothed over time by water action tumbling it against other stones, sand and bedrock before depositing it on ancient or current river beds, shorelines, or other geological formations.
Gravel may be multi-colored or more uniform in color depending on the type of bedrock from which it came. Its size often determines its use and what it is called – pea gravel, river gravel, washed gravel, and river rock of various sizes. Gravel can also be crushed into smaller pieces for different purposes, and is referred crushed gravel as some edges are still smooth.
Crushed stone is just that, large pieces of bedrock mechanically crushed into smaller sizes and grades at quarries. It has rough angular faces with jagged broken edges and is usually made from bedrock native to the area it is being harvested from. It could be sedimentary (limestone, dolomite, shale, sandstone), metamorphic (slate, gneiss, marble, metaquartzite), or igneous rock (granite, trap rock, basalt, or pumice). Its color is often more uniform depending on which type of bedrock it is taken from.
Types Of Gravel
There are different types of gravel based on the location it is taken from and its physical size. Gravel is naturally occurring and has smooth faces and rounded edges. It may be taken from river beds or other deposit areas and passed through screens with different sized openings. The opening size determines if the gravel is pebble, cobble, or boulder sized.
The screens divide the pebbles into very fine (0.08” to 0.16”), fine (0.17” to 0.32), medium (0.33 to o.63), course (0.64” to 1.26”), or very course (1.27” to 2.52”). Different sizes are used for different purposes. Larger gravel between 2.53” and 8” is called cobbles, and anything larger is referred to as boulders.
River rock is typically natural gravel that has smooth rounded surfaces due to water action. It ranges in size from 3/8” to 5” and has a diverse color range depending on the rock’s origin and is used for practical and decorative purposes. It can also be artificially tumbled and polished with machinery, but usually costs more.
Small river rock is smooth and rounded and tends to be more friendly on feet, hands, and knees, making it ideal for paths and playgrounds, but it can also be slippery. Larger diameter gravel is often used for fountains, water or drainage courses, waterfalls, or other water features. The rocks are usually sold by the ton or truckload depending on the size, with smaller sizes also sold by the bag.
Crushed gravel is not crushed stone although it may be used for similar purposes. Crushed gravel typically is fragmented gravel in its natural form from current or ancient river beds and shoreline deposits. It has rounded surfaces with broken or chipped faces or edges, making it coarse. It has a broader color spectrum than crushed stone and is lighter and often less expensive.
Crushed gravel can range in different sizes too and is often used for driveways, paths, and decorative purposes. It commonly ranges from 0.63″ to 1.26” in diameter and is commonly sold by the ton or truck-load.
Pea gravel is small, pea-sized gravel 1/8” to 3/8” in diameter. It may have rounded or angular edges depending on where it is obtained or ‘created’. Its blend of colors ranges from browns, rusty reds, tans, grays, whites, and sometimes greens or grayish blue depending on where it originates.
Pea gravel is often used for playgrounds, walkways, between paving stones, for gardens to inhibit weeds and retain moisture, and around building perimeters to keep rodents from burrowing. Due to its small size, pea gravel spreads out so containment edging is recommended. It is usually sold in 50-pound bags or by the ton.
Lava rock is broken into different sizes and used for similar functions to gravel and crushed stone. It is available in reds, blacks, browns, grays, or mixtures of those colors. It typically has broken edges, but naturally or mechanically tumbled pebbles or rocks are available too.
The porous nature of the rock makes it ideal for water retention in gardens and planters, plus it can be used if fire pits or for decorative purposes. It is commonly sold by the bag, but larger quantities are available in some locations.
Marble chips are a byproduct of the marble industry. Waste material is crushed into small pieces or chips and used for decorative and utilitarian functions. The chips have broken edges and a common color range depending on the quarry they come from. They can be used for gardens, planters, walkways, and even driveways.
The chips help prevent weed growth and help soil retain water, plus they look great and sparkling in the sunshine. Marble chips are available in 10- to 50-pound bags, or by the ton.
Gravel/Crushed Stone Size Chart
The term gravel is often used when referring to crushed stone, but they aren’t the same thing. So, if you are looking for a specific size of crushed stone, the Table below will help identify the grade and size you may want. However, it is best to check the grade size for the local quarry as some grades may differ.
|#1||2” – 4” wide|
|#2||1/2” – 3”|
|#3||1/2″ – 2” wide|
|#5||1” or less|
|#8||3/8” – 1/2″|
|#10||1/4” or less|
|#67||Less than 3/4″|
|#411||#57 with stone dust|
Types and Grades of Crushed Stone
The types and grades of crushed stone identify the sizes of crushed stone, which in turn helps determine its uses. It should be noted, though, that different quarries use different sizing for various grades, so always check with your supplier.
Gravel dust, which helps with compaction, is available with most grades upon request. The following descriptions identify the grades of crushed stone, sizes, and common uses.
This is the largest grade of crushed stone with stones between 2” and 4”. It’s used for filling large holes, preventing erosion, slope protection, lining sewer trenches and septic projects, rough road grading, culvert ballast, lining drainage ditches, etc.
This grade varies in size with the supplier and contains rocks ranging from 1/2″ to 2-1/2” or 3” in width. It is often used as the base material for driveways, worksite access roads or pads, farm roads, highways, railroad ballast, and for filling large holes as the different sizes compact well to form a solid base.
Similar to #2 but with a more standard 1/2″ to 2” width. It is used for driveway and roadway base material, railroad and culvert ballast, filtration for septic systems, dry wells, and to manage stormwater erosion. It both compacts and drains well.
This size is commonly used for road bases, driveways, unpaved roads, as a base under pavers, for drainage projects, fill, or railway ballast. It contains stones 1” or 1-1/2” or smaller in width depending on the supplier.
This grade contains stones between 3/8” and 1/2″ in size. It is used for bio-retention ponds, bedding for septic tanks, filtration, and backfill for retaining walls and weeping tile. #8 is also used in the production of ready-mix and asphalt and for building applications, plus topping driveways, landscaping, and environmental erosion protection.
This is the finest screening grade and contains gravel dust and chips 1/8” or 1/4” and smaller depending on the supplier. A crushing process byproduct, it is often referred to as the screenings and can look like coarse sand. It is used to manufacture concrete blocks, pavers, and precast concrete products. It is also used as a leveler for pavers and brick patios or stabilizing large rocks, and as a finishing layer for foot and bike paths.
One of the most common grades, it contains stones between 1/2” and 1” with an average of 3/4″. It can be shoveled and spread easily for use in driveways, parking areas, paths, walkways, drainage control, and landscaping. It is often used to line underground pipe and cable trenches, over weeping tile, and is used as an aggregate in concrete and asphalt.
This grade usually ranges from 1/2″ to 3/4″ in size and can easily be shoveled, but has minimal compatibility as it excludes pea gravel and stone dust. It is used under concrete slabs, for drainage, fill, backfill, driveways, and walkways, and to stabilize soil. It is also used in premixed concrete, as a base layer for retaining walls, pavers, culverts, and in hot-mix asphalt.
Another common grade, #411 is similar to #57 in stone size but also contains the screenings or stone dust from the crushing process. The screenings make this grade very compactable for a solid, stable base. It is typically used for driveways, walkways, parking areas, under concrete floors, or for paver and wall bases – anywhere compactable crushed stone is required.
Washed vs Unwashed Gravel
Unwashed gravel often has clay, silt, sand, or dirt stuck to it, which can also bind smaller stones or pieces of crushed rock to it. The attached debris helps the rocks stick together, making them more compactible, but also less effective for drainage use.
Washed gravel has all that material washed off it so it is cleaner and smoother. It is often used for landscaping or garden cover as it contains little if any organic material.
The term washed gravel also often includes crushed stone that has had the dust from the crushing process washed off. The washing process can soften broken edges as well as clean the stones, giving them a more pebble-like look, such as pea gravel or river rock. Washed crushed stone is commonly used for drainage and landscape purposes.
How to Choose Right Gravel Type for Your Project
Selecting the right size of gravel or crushed stone for your project can be difficult. The Table below identifies the types or grades commonly used for different projects.
|Location||Type of Gravel/Crushed Stone|
|Shed Base||#5, #8, #57|
|Under Deck||#5, #8, pea gravel, river rock|
|Driveway||#5, #8, #57, #67 #411|
|Patio||#10, #67, pea gravel, marble chips|
|Paver Base||#10, #411|
|Landscaping||#1, #2, #5, #8, #57, #67, pea gravel, river rock, marble chips, lava stone|
|Retaining Walls||#5, #8, #57, #67 #411|
|Garden Path||#5, #8, #57, #67 #411, pea gravel, marble chips|
|Pole Barn||#10, #67, #411|
|To Make Concrete||#8, #57,|
|Under Concrete Slab||#57, #67, #411|
|Crawl Space||#5, #8, #57, #67|
|Drainage Around House (French Drain)||#5, #8, #57,|
|Horse Stalls||#8, #57, #67, pea gravel|
|RV Pad||#5, #8, #57, #67 #411|
|Fire Pit Area||lava stone, pea gravel, river rock|
|Window Well||#5, #8, pea gravel, marble chips, river rock|
Gravel and crushed stone are often used interchangeably both as terms and purposes. Water-smoothed gravel has softer-feeling surfaces and edges and is often used for decorative and utilitarian functions. Crushed stone, while sometimes used decoratively, is more frequently used for utilitarian building purposes.
Using #5, #8, or #57 grade crushed stone will produce a functional driveway. However, a walkway or path of fine or medium pea gravel will not only be functional, but aesthetically pleasing too.
Hopefully, you have a better awareness of the differences between gravel and crushed stone, their sizes, grades, and uses, and are better prepared to make the best choice for your project.