About the Crusher Run Calculator
Crusher run is crushed stone straight from the crusher, with every size from about ¾ inch down to fine dust left in. Because the fines fill the gaps between the larger stones, it packs into a dense, hard layer when it is dampened and compacted. That makes it the standard base under gravel driveways, paver patios, sheds, concrete slabs and walkways. Depending on where you live it may be called quarry process (QP), dense grade aggregate, road base, Type 1 or 21A.
The catch is that crusher run shrinks. A loose layer spread from a truck loses a good part of its thickness under a plate compactor, so ordering by the finished depth leaves you short. This crusher run calculator works from the finished, compacted depth you need, adds a compaction allowance to find the loose volume to order, converts it to tons, and tells you how deep to spread it and how many separate lifts to compact.
How to Use the Crusher Run Calculator
Enter the length and width of the base in feet.
Enter the finished compacted depth in inches.
Enter the compaction allowance, usually 15 to 25%, and optionally the price per ton.
The Formulas
compacted yd³ = length × width × depth ÷ 12 ÷ 27
loose yd³ = compacted yd³ × (1 + allowance)
tons = loose yd³ × 1.5
loose depth = finished depth × (1 + allowance)
lifts = ⌈loose depth ÷ 4 in⌉Step-by-Step Example
A 20 × 12 ft shed base, 4 inches compacted, 20% allowance, at $35 a ton.
compacted 20 × 12 × 4 ÷ 12 ÷ 27 = 2.96 yd³
loose 2.96 × 1.2 = 3.56 yd³
tons 3.56 × 1.5 = 5.33 tons
spread 4 × 1.2 = 4.8 in loose → 2 lifts
cost 5.33 × $35 ≈ $186.67Why Compaction Matters
A well-compacted base spreads loads evenly into the soil and does not settle later. If crusher run is laid loose, wheels and foot traffic slowly push it down, leaving ruts in a driveway, sunken pavers or a shed that rocks on its base. Compaction squeezes out air, locks the angular stones together with the fines, and gives a surface hard enough to walk on without leaving footprints. Most of that shrinkage happens in the first few passes of the compactor, which is why the allowance is fairly predictable for a given material.
Spreading in Lifts
A plate compactor can only firm up a few inches of stone at a time. Spread a thick layer in one go and the top becomes hard while the bottom stays loose, settling months later. The usual practice is to spread no more than about 4 inches loose, compact it with several passes in different directions, then add the next lift. A heavier roller or rammer can handle thicker lifts, so follow the guidance for your machine. The calculator counts lifts at 4 inches loose.
Moisture
Crusher run compacts best when it is damp but not wet. The water lubricates the fines so they move into the gaps, and as it dries the layer becomes very hard. If the stone arrives dry, mist it with a hose before compacting each lift. Too much water turns the fines into mud that squeezes up around the compactor plate. Many contractors aim for stone that holds together briefly when squeezed in the hand, without water running out.
Preparing the Ground
Remove grass, topsoil and roots, which rot and leave voids. Compact the exposed subsoil, and on soft clay lay a woven geotextile to stop the crusher run being pushed into the ground over time. Slope the base slightly so water runs off, about a quarter inch per foot for patios and more for driveways. Edge restraints, timber forms or a dug trench keep the stone from spreading sideways as it is compacted.
How Deep to Build
Paths, patios and shed pads usually need about 4 inches of compacted crusher run over firm soil. Paver patios that will carry a hot tub or vehicles need 6 inches or more. Driveways typically use 6 to 8 inches, or a layer of larger base stone with crusher run on top. Poor, wet soil calls for deeper bases and fabric.
Crusher Run Under Pavers and Slabs
Under a paver patio, crusher run forms the structural base, with about an inch of coarse sand on top to bed the pavers. Under a concrete slab, it provides an even, well-drained support that stops the slab cracking where soft spots would otherwise be. In both cases the base should extend about 6 inches beyond the finished edge so the edges are fully supported. Add that margin to your length and width before calculating.
Renting a Compactor
A plate compactor can be hired by the day from most tool rental shops. Forward-only plates suit small patios and paths; reversible plates are heavier and better for driveways and deeper bases. Make several overlapping passes over each lift, working from the edges toward the middle, until the surface no longer shows footprints. Wear hearing protection and steel-toed boots, and keep the plate away from walls and foundations that could be damaged by vibration.
Understanding Your Result
The headline gives the tons of crusher run to order.
The volume line shows the compacted and loose cubic yards.
The spreading line gives the loose depth and the number of lifts.
The cost line multiplies the tons by your price.
When Should You Use This Calculator?
Use it when building a base for pavers, a shed, a slab or a driveway.
Use it to check that a supplier's quote allows for compaction.
Use it to plan how many passes and lifts the job will take.
Common Mistakes
Ordering by finished depth. Allow 15 to 25% for compaction.
Compacting one thick layer. Spread and compact in 4-inch lifts.
Compacting dry stone. Dampen it first.
Building on topsoil. Strip to firm subsoil before spreading.