Gravel and Crushed Stone Calculator: Tons, Cubic Yards and Bags

Worked example

These are the figures the calculator opens with and the answer it gives. Change anything above and every number below moves with it.

What this calculator assumes

• Aggregate is bought by the ton and placed by the compacted cubic yard, and the number that joins the two is a density that varies by quarry. This page computes the compacted volume in place and multiplies it by a conversion factor in tons per compacted cubic yard.
• The conversion factors and the compacted to loose expansion percentages come from Wisconsin DOT and Wisconsin Highway Research Program report 0092-22-05, which measured them for nine named materials and published each one as a range rather than as a single figure. The page uses the midpoint and prints the range beside it.
• If you buy by the ton, compaction does not change your order: the tonnage is the compacted volume times the factor either way. If you buy by the loose cubic yard it does, because a loose yard on the truck becomes less than a yard in the ground, and the expansion percentage is what tells you how much less.
• Depth is the compacted depth of the finished layer, not the depth of the loose material before it is rolled.
• Bag counts are for the half cubic foot bags sold at the box stores, and they are figured on the loose volume, because a bag holds loose material.
• The figures were measured in Wisconsin. The report itself notes that only about 23 percent of the DOTs it surveyed use conversion factors for aggregates at all, and that some materials needed region specific factors. Put the figure from your own delivery ticket in the last field and the page uses that instead.

Tons or yards, and why you need both

The quarry weighs the truck, so the ticket says tons. The plan says depth, so the job is measured in compacted cubic yards. Everything that goes wrong with a gravel order happens in the gap between those two units, and the number that closes it is a conversion factor in tons per compacted cubic yard.

That factor is not a constant. Wisconsin DOT and the Wisconsin Highway Research Program measured it for nine named aggregates in report 0092-22-05 and found the whole set ran from 1.50 to 1.98 tons per compacted cubic yard. At one end, structure backfill of sand and gravel. At the other, dense graded crushed base in the 1 1/4 inch size. Use one figure for both and a 20 ton order is out by 6 tons.

So this page asks which material, prints the published range beside whichever figure it used, and leaves a field for the number on your own delivery ticket. Put that in and the answer stops being an estimate.

The same pile has three different volumes

Aggregate passes through three states on the way to the job, and the report names all three: bank, which is the material still in the ground or in the face; loose, which is stockpile and hauling; and compacted, which is what you are paid for. A cubic yard in one state is not a cubic yard in another.

Compacted to loose runs from 27 to 60 percent depending on the material, which is the number almost nobody publishes. Breaker run swells 27 to 30 percent. Recycled concrete base swells 37 to 60. That is the difference between a full load and two trips.

Which one matters to you depends entirely on how you buy. If you buy by the ton, compaction does not change your order at all: compacted volume times the compacted conversion factor is the tonnage either way, and the scale does not care how fluffy the pile was. If you buy by the loose cubic yard it changes everything, because the yard you pay for on the truck is not the yard that ends up in the ground.

Why a range and not one clean number

A single figure would be easier to read and it would be worse. The report published each factor as a range because that is what the testing produced, and the spread is real: a quarry in one region and a quarry in another are not selling the same rock, and the report found that some of these materials needed region specific factors.

It also found that only about 23 percent of the state DOTs it surveyed use conversion factors for aggregates at all. Most of the industry is working off whatever number the yard says. Getting a measured range and knowing how wide it is beats getting a confident figure from nowhere.

These are Wisconsin numbers and this page says so on the page rather than in the small print. They are the best free published figures available, and they are not the figure for your quarry. The ticket is.

What the depth is actually measuring

Depth here is the finished compacted depth of the layer, not the height of the loose pile before it is rolled. Enter the layer you want to end up with and the page works backwards to the truck.

A driveway base is usually 4 to 8 inches of crushed material over fabric, a patio or paver base 4 to 6, and a french drain or a trench backfill is whatever the detail says. Under 2 inches compacted, no aggregate holds together under a wheel load, and the page says so.

Anything over about 4 inches goes down in lifts, because a plate compactor cannot reach the bottom of a deeper layer. Two four inch lifts compact properly. One eight inch lift settles later, usually in a wheel track, usually after you have been paid and gone.

Questions people ask

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