The gravel calculator above converts an area and a depth into the three numbers a materials yard understands: cubic yards, tons, and money. It carries a density selector with published values for common construction aggregates, a waste factor, a bag-count output for small jobs, and a delivery charge line, so the figure on screen is the figure you can quote down the phone.
Arb Digital publishes it as one page rather than ten. Pea gravel, crushed stone, road base, ballast and river rock are the same calculation performed with a different density, and separating them into a page each would produce ten near-identical calculators competing with one another. Change the aggregate in the selector and the density changes with it. Everything else is untouched.
What This Gravel Calculator Does
It computes placed volume, converts that volume to weight using a density you can see and edit, applies a waste factor, and rounds the result up to something you can actually order. Bulk aggregate is quoted per ton and delivered by the truckload, so the tool rounds the tonnage up to a sensible ordering increment and reports the raw figure beside it. For small quantities it also converts the requirement into bags at whatever bag weight your supplier stocks.
This is a bulk aggregate tool, not a landscape mulch tool. Our mulch calculator covers bark and wood mulch, which is a completely different material — light, organic, sold by the bag or the scoop, applied at a depth chosen for weed suppression rather than load bearing. That is the boundary: mulch is a ground cover with a density under a tenth of stone, and mixing the two up will produce an order that is wrong by an order of magnitude.
How to Use It
- Choose units and aggregate. The selector loads a published density. If your material is not listed, choose "Other" and type the weight from your supplier's ticket into the density field.
- Pick the area shape. Rectangle for a driveway or patio, circle for a fire-pit surround or a tree ring, or enter a known area directly if you have already measured an irregular shape.
- Enter the depth. This is the finished, placed depth, in inches or millimetres. A base course under pavers and a decorative top dressing are very different depths for the same footprint.
- Set the waste factor. Ten percent is a reasonable starting point. Raise it where the ground is uneven or the edges are undefined, because both swallow material invisibly.
- Add price and delivery. Price is per ton or tonne. The delivery field is a flat charge added at the end so the cost figure reflects what you will actually pay.
The Formula / How It's Calculated
The chain is short. Area is length × width, or π × (diameter ÷ 2)², or whatever you entered directly. Volume = area × depth, with depth converted from inches to feet or millimetres to metres first — this is the step people get wrong, because a four inch depth is 0.333 feet, not 4. Volume in cubic feet is then divided by 27 to give cubic yards.
Weight is volume in cubic yards × density in pounds per cubic yard ÷ 2,000 to give US short tons. The waste factor multiplies the tonnage, and the order figure is that result rounded up. Bag count is ceil(total pounds ÷ bag weight). Cost is order tonnage × price plus the delivery charge.
The densities built into the selector come from Exhibit 620-1 of the WSDOT Design Manual, Chapter 620 Design of Pavement Structure, which tabulates unit dry weights for gravel base and surfacing materials both as loose truck measure and as compacted on the roadway. Gravel base is listed at 3,400 to 3,800 pounds per cubic yard compacted, with 3,700 recommended as the most suitable factor; ballast is 3,900 compacted and 3,100 loose; permeable ballast is 2,800 compacted. The same exhibit notes that the weights are dry weights requiring correction for water content, and that stockpiled material should be increased by 10 percent to allow for waste.
Loose Weight and Compacted Weight Are Not the Same Number
This is the detail almost every aggregate calculator on the web skips, and it is worth more than everything else on this page. A cubic yard of crushed surfacing base course weighs about 2,950 pounds sitting loose in the back of a truck, and about 3,700 pounds once it has been spread and compacted in place. That is a 25 percent difference in the same material.
The practical consequence: if you measure the hole you need to fill and you intend to compact the material into it, you must buy enough material to fill that space at the compacted density. Use the loose figure and you will be a quarter short. The selector lists both states explicitly for the materials WSDOT publishes both for, so you can pick the one that matches what you are doing. For a decorative top dressing that will never be compacted, the loose figure is the right one. For a paver base, a driveway or anything structural, use the compacted figure.
Water content moves the number too, in the opposite direction from what people expect. The published values are dry weights. Wet aggregate weighs more per cubic yard, so a wet load contains less stone per ton than a dry one. Buying by weight after rain means paying for water — not usually enough to matter on a garden path, very much enough to matter on a driveway.
Why We Did Not Build Ten Separate Aggregate Pages
There is a common pattern in calculator sites of publishing a page for pea gravel, another for crushed stone, another for limestone, another for river rock, another for road base, another for sand, another for topsoil, and so on. Each page contains the same three inputs and one different constant. The pattern exists because ten pages can rank for ten phrases.
The problem with that from a user's point of view is that the constant is the only thing that varies, and it is the thing you most need to be able to see and question. Hiding it inside the page means you cannot check it, cannot compare it against your supplier's ticket, and cannot use the tool at all if your material is not one of the ten. Putting it in an editable field with a cited source solves all three. If your yard tells you their 3/4 inch minus runs at 2,700 pounds per cubic yard, type 2,700 — their scale is more authoritative than any published table for the specific stone they are selling you.
That is also why we do not publish invented densities for pea gravel and river rock. Those figures vary with stone type, gradation and moisture, and the honest answer is to use the number on the delivery ticket rather than a number we made up to fill a row in a table.
Depth Is Where the Money Is
Cost scales linearly with depth and there is no rounding to hide behind. Going from a 3 inch base to a 4 inch base on a 200 square foot patio raises the requirement by a third. Going to 6 inches doubles it. Because aggregate is heavy and cheap per ton but expensive to deliver, the difference frequently shows up as a second load rather than a slightly bigger first one.
Sensible depth depends on what the surface has to carry. A decorative dressing over landscape fabric might be 2 inches. A pedestrian paver patio commonly uses a compacted aggregate base — the CMHA Guide Specification for the Construction of Interlocking Concrete Pavement requires base compaction to not less than 98 percent of ASTM D 698 Proctor density for pedestrian areas and residential driveways. A vehicle driveway needs more depth than a footpath, and soft or clay subgrade needs more again. Our paver calculator handles the full paver build-up including base and bedding layers if that is the job.
Compaction, Subgrade and the Volume That Disappears
Two things eat aggregate that a flat volume calculation does not capture. The first is compaction itself: loose material placed at 6 inches will finish at less than 6 inches once it is plate-compacted, and the difference has to come from somewhere. The second is subgrade. Aggregate placed on soft ground pushes down into it. On a well-drained sandy subgrade this is a rounding error; on wet clay it can be inches, and the material simply vanishes into the ground.
Neither is something arithmetic can predict from a length, a width and a depth, which is exactly why the waste factor field exists and why it is editable. Ten percent handles ordinary spread and spill on firm ground. Fifteen to twenty percent is more realistic on soft subgrade or where the edges are unrestrained and the stone can migrate outwards. Where the ground is genuinely poor, a geotextile separation layer stops the aggregate disappearing into the subgrade at all, and that is a cheaper fix than buying more stone every year.
Ordering: Tons, Yards, Bags and Minimum Loads
Aggregate is sold by weight in some markets and by volume in others, and the same yard will often quote both. This tool gives you the volume and the weight side by side so you can order in whichever unit the supplier uses without re-deriving anything. Use the cubic yard calculator if you need to convert a volume you already have, and the square footage calculator if the area itself is the awkward part.
Bagged stone is convenient and expensive. At a typical 50 pound bag, a single ton is 40 bags — which is a lot of lifting for material that costs a fraction of the price loose. The crossover point where bulk delivery becomes cheaper is usually well under a ton once you count the delivery charge, which is why that field is on the form. Below the crossover, bags win on convenience; above it, bags stop making sense quickly.
Common Mistakes to Avoid
- Using inches as feet — a 4 inch depth is 0.333 feet, and treating it as 4 overstates the order twelvefold.
- Using the loose density for a compacted layer — compacted aggregate is roughly a quarter heavier per cubic yard, so the loose figure under-orders badly.
- Applying a mulch density to stone — bark mulch and crushed rock differ by roughly an order of magnitude in weight per cubic yard.
- Ignoring the subgrade — soft or wet ground absorbs aggregate, and no waste factor set from a spreadsheet can predict how much.
- Forgetting the minimum load charge — a small order can cost the same as a much larger one, so it is often worth checking the price of the next size up.
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Pair this with the paver calculator for a full patio build-up, the concrete calculator where the aggregate is going under a slab, the mulch calculator for organic ground cover, the cubic yard calculator for volume conversions and the density converter if your supplier quotes in a unit the form does not take. The free online tools hub lists every calculator we publish.
Frequently Asked Questions
That area is 200 square feet, which at 4 inches deep is 66.7 cubic feet or 2.47 cubic yards. At the WSDOT compacted gravel base figure of 3,700 pounds per cubic yard that is 4.57 tons raw, and just over 5 tons once a 10 percent waste factor is applied.
It depends on the material and whether it is loose or compacted. WSDOT publishes gravel base at 3,400 to 3,800 pounds per cubic yard compacted, with 3,700 recommended; ballast at 3,900 compacted and 3,100 loose in the truck; and permeable ballast at 2,800 compacted. These are dry weights.
Because the same aggregate occupies less space once compacted. Crushed surfacing base course is about 2,950 pounds per cubic yard loose and about 3,700 compacted. If you are filling a measured space and then compacting it, you need the compacted figure or you will be roughly a quarter short.
Choose "Other aggregate" and type the density from your supplier's ticket into the density field. That is the right approach for pea gravel, river rock, decorative stone, riprap and topsoil, whose weights vary too much by source for a published table to be reliable.
It depends entirely on what the surface carries. A decorative dressing may be a couple of inches; a paver base or a driveway needs considerably more, and soft subgrade needs more again. Depth requirements come from the pavement design or the paver manufacturer's specification, not from this tool.
Bags suit small quantities where handling matters. At a 50 pound bag it takes 40 bags to make a ton, so bulk delivery is normally cheaper well before that point once the delivery charge is included. The tool shows both figures so you can compare.
Mulch is organic ground cover and weighs a small fraction of what stone weighs per cubic yard, so it is priced, delivered and applied differently. Use the mulch calculator for bark and wood chip, and this one for stone, sand and road base.
Yes. The published densities are dry weights, and WSDOT's own note requires a correction for water content. Buying aggregate by weight after heavy rain means part of what you pay for is water rather than stone.
This tool produces material estimates only. Pavement thickness, subgrade preparation and compaction requirements are governed by the project specification and local code, and must be confirmed by a qualified professional.
