Crusher Run Calculator for Compacted Base Depth
Enter your project dimensions
Red Piedmont clay holds water for days after a summer thunderstorm, and a base laid over it gives a little under the first loaded trailer that crosses. That is the correction this crusher run calculator exists to make. The depth you type in has to be the depth the layer finishes at once it has been rolled, not the loose depth you could measure with a tape the morning it lands.
A 24 by 14 parking pad beside a Southside farm lane
Take a pad meant to hold a pickup and a small utility trailer off the edge of a clay lane. The example is hypothetical, but the arithmetic is the arithmetic the tool does.
The pad is 24 ft by 14 ft, so 336 square feet. Because it carries vehicles rather than feet, the finished compacted depth is 6 inches. Six inches is half a foot, so 336 x 0.5 gives 168 cubic feet of stone. Twenty-seven cubic feet fill a cubic yard, and 168 divided by 27 is 6.22 cubic yards. Dense-graded base weighs about 3,000 lb a cubic yard on this site, which is 1.5 tons, so 6.22 x 1.5 comes to 9.33 tons. With the extra-quantity box ticked the figure moves to 10.3.
Ten tons is the sensible order. Place it in two lifts of roughly 3 inches rather than one 6-inch layer, mist each lift before the plate compactor goes over it, and keep the odd wheelbarrow-load back. Damp dense-graded stone binds far tighter than dry, and on clay that difference shows up the following spring.
Putting that pad through the shape, depth and material boxes
The shape row decides how the area is read. Rectangle takes a length and a width in feet. Circle takes a diameter in feet, which suits a turnaround or a round pad. Multiple areas holds up to five separate entries, so a lane that changes width partway along can be split into straight runs instead of averaged into one guess.
Depth (inches) accepts anything from 0.25 to 24. For a base course that means 4 inches under a path or a paver field, 4 to 6 under a car drive, and 6 to 8 where a loaded truck turns. The material select is what converts volume to weight, so it has to match what you are actually ordering. The tick box marked for compaction and spillage adds 10 per cent to the result; it is ticked when the page loads, and you can untick it if you would rather decide the margin yourself.
Press calculate and three figures appear together: cubic yards, tons and cubic feet. Email my quote sends that set to your inbox so the numbers survive the walk back to the house.
Why 6.22 yards and 9.33 tons describe one pile
Cubic yards answer a question about space: whether the pile will sit clear of the septic field, and whether the excavation you dug will swallow it. Tons answer a question about loading, which is the unit the order is written in. Cubic feet earn their keep when you are patching a washout rather than building a pad, because a 2 ft by 3 ft dip at 4 inches is 2 cubic feet and no more.
The three move together because the material weight is fixed. Change the material select and the tonnage changes while the yardage does not: the same 6.22 yards of screenings runs nearer 2,900 lb a yard, and the same volume of clean #57 stone comes in lighter at about 2,800 lb.
The 10 per cent tick, and when the extra belongs in the depth box instead
Ten per cent covers spillage off the wheelbarrow and the stone that disappears into the first roller pass. It does not cover a soft subgrade. Where wet Piedmont clay pumps under the plate, the stone you lose goes down into the ground, and the honest fix is another inch or two in the depth field plus a geotextile layer sourced from a landscape supplier, not a percentage.
On anything lane-sized, round the calculated tonnage up to the next whole ton. A surplus of base stone is the material you patch the first rut with. A shortfall leaves an unrolled strip open to the next storm while a second load is arranged. On a small shed pad you can take the lower figure, since that layer is not carrying a wheel load.
21A or 21B under the load you are putting down
Both Virginia dense-graded sizes sit on the same weight line, so the tonnage does not change between them. The choice is about how the layer behaves.
- 21A carries more fines and packs the tightest, which is why it is the standard base under drives, parking pads and shed and patio slabs.
- 21B is the coarser size with fewer fines. It sheds water a little better and locks up a little less, and it is the crusher run product this calculator sends you to.
- Screenings belong in a thin leveling skim over a compacted base, never as the base itself.
- Keep dense-graded stone out of a French drain entirely. The fines that make it bind also hold water, so #57 stone or drain rock does that job.
- A patio is not a pad. The base under a paver field runs past every exposed edge and sits under a bedding layer, so it is sized on its own tool, and the surface stone over the base on another again.
What the ground under the pad does to the depth you enter
West of the Blue Ridge the limestone valleys often put bedrock within a foot or so of the surface, so an excavation can stop shallower than planned. Measure what you actually achieved and enter that, and spread runoff rather than channeling it into one spot on karst ground.
On the flat Coastal Plain of Hampton Roads, the Eastern Shore and the Northern Neck, water has nowhere to run. Raising the pad above the surrounding grade and giving it somewhere to drain does more than extra inches of stone. Across the Piedmont the base is doing structural work over clay that drains slowly, which is where the 6-inch figure earns its place. Frost depth here is set locality by locality, from about 12 inches at the coast to about 24 in the northern counties, so check your own before planning anything that has to sit below it.
When the tonnage looks right, open the product page, set your quantity and date, and let delivery sort itself by ZIP at checkout; check delivery by ZIP covers what the truck needs at the drop spot.
Common questions
My pad is an odd shape with a curved edge. How do I get a number out of it?
Break it into rectangles you can measure and enter them under multiple areas, up to five. For a curved end, take the widest and narrowest measurements across it and use the midpoint as the width. Base stone is forgiving of a small overestimate and unforgiving of a short one, so let the rounding fall upward.
The drive already has stone on it and only needs bringing back up. What depth do I enter?
Set a straightedge across the low patches, measure down to the existing surface in several places, and enter the average of those gaps rather than a full base depth. A topping pass is usually 1 to 2 inches, and the depth field goes down to a quarter of an inch, so a thin skim is still measurable.
What actually goes wrong if I order half a ton short?
The last strip stays uncompacted while a second load is arranged, and on clay that strip takes rain straight into the subgrade. The join between an old rolled section and a fresh one also stays visible, because the two halves never key together the way a single continuous placement does.
Will the tonnage hold up once the subgrade turns out uneven?
The volume side is exact arithmetic on the dimensions you type. The variance sits in the ground: a wavy excavation floor, a soft patch that swallows stone, and the compaction you achieve all move the real figure. Probe the depth at four or five points across the pad, average them, and the result is sound enough to order from.
Which product page do I go to once I have the tonnage?
The crusher run product on this site is 21B. If what you want is the tighter-packing base under a drive or a slab, go to 21A instead. The two sit on the same weight line, so the tonnage the calculator gives you carries across to either page unchanged.
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