Site Work Calculators

Site work is the one section where the arithmetic is trivial and the number you actually need is not published anywhere.

The calculators

• Gravel CalculatorSolid rock density derived from WSDOT's own riprap equivalences
• Sand CalculatorFour WSDOT fine aggregate gradings, and the sieve that separates them
• Topsoil CalculatorWSDOT 9-14.2, where two of three topsoil types are defined by provenance

Volume is length times width times depth. There is no code table, no manufacturer data sheet and no room for disagreement. Every calculator on the internet gets the cubic yards right.

Then they all convert to tons, and none of them cite anything. That is not laziness. After a long look, there is nothing to cite: state DOT specifications describe what an aggregate must ACHIEVE, gradation and wear and specific gravity, and they do not tabulate what a heap of it weighs, because the weight of a heap is a property of the heap rather than of the product.

What can be pinned down

The rock. WSDOT sizes riprap by naming a weight and a volume for the same stone, twice over, and both come out at about 149 lb per cubic foot. That is solid stone with no air in it, and it is a real anchor: whatever your material weighs, it weighs less than that.

How much less is the void fraction, and it moves with the gradation, the moisture and how the pile was tipped. A third is a common working figure and it is a guess. The pages here show the anchor and the arithmetic and leave the density to the person who actually weighs it.

The allowance that catches people out

Base course is delivered loose and compacted in place, so the depth that arrives is not the depth you keep. Order the finished volume and the compactor takes your margin, which is how a small job ends short with the driver already gone. That allowance is an input here and it is labelled as ours.

Two questions worth asking the yard

What does a cubic yard of this weigh, and are you selling by weight or by volume? The first has a real answer because they run loads over a scale all day. The second decides whether the figure you calculated is the figure you order. And if the answer is a scoop, ask what a scoop is: it is whatever their loader bucket holds, and it varies between yards.