Stone Calculator: Pick the Grade, Then the Depth, Then the Tons

Two kinds of people open this page. One has a line on a plan that reads #57 and wants to know how many tons that is. The other has a corner of the yard that holds water after every storm and wants to know what to put in it and how deep. The table below answers the second question, the calculator answers the first, and the grade you choose changes both the depth and the weight.

Depth by job, from a path top course to a trench at the toe of a slope

These are the depths worth entering for common work on a Georgia lot.

Depth is the number that moves the order most, and on red clay it is usually the one people trim. A drive top course at 2 inches over a firm base is fine; the same 2 inches straight onto clay disappears into it by the second wet month.

Putting a trench, a pad or a round rain barrel base into the form

Rectangle takes a length and a width in feet. For a trench, the width is the trench width, so 18 inches goes in as 1.5. Circle takes a diameter in feet, which handles a round pad under a rain barrel or a ring of stone at a downspout. Multiple areas holds up to five pieces, so a drain line plus the splash pad at its outfall is one calculation.

Depth is entered in inches, anywhere from 0.25 to 24. Anything deeper than two feet goes in as two entries and gets added by hand, which comes up on a retaining wall backfill more often than you would think. Choose the grade from the material list, decide on the box marked add 5% extra for compaction and spillage, and press the button. Cubic yards, tons and cubic feet come back together, with an option to have them emailed.

What #57, #67, #89 and #4 actually measure

The grade number describes a size range, and the lower the number, the bigger the rock. #4 runs 3/4 to 1-1/2 inches. #57, which around here is usually crushed granite, runs 3/16 to 1 inch and is the everyday drainage and driveway size. #67 is smaller at 1/4 to 3/4 inch, which is why it sits so well around a pipe. #8 is about 3/32 to 3/8 inch, and #89 runs from 3/8 inch down into fines, so it suits paths, joints and a finish course. Screenings are dust and small chips that screed into a firm bed. Railroad ballast is angular 1 to 2.5 inch rock that locks together under weight while water still runs through it.

GDOT specifies crushed stone by size number, which is why a plan drawn here will say #57 rather than describing the rock. If a line item is not clear, check the size range against the list above before you order rather than after.

Clean stone drains, stone with fines binds

This is the decision that goes wrong most often, and no amount of correct arithmetic saves it. Washed, clean material such as #57 granite has open voids that let water move, which is what a French drain or a run behind a wall needs. Crusher run and graded aggregate base have their fines left in, and those fines pack tight under a plate, which is what a driveway base needs.

Swap them and both jobs fail quietly. Fines-rich stone in a drain silts up and holds the water it was meant to carry away. Clean stone under a drive keeps shifting under a tire because there is nothing binding the pieces. Over Piedmont clay, put non-woven fabric in the trench before the stone so the red clay around it cannot wash into the voids and close them.

A trench drain at the toe of a slope, and a path top course

Two made-up jobs, written out so you can follow the math.

A drain trench at the bottom of a sloping back yard, 45 feet long and 18 inches wide, filled 14 inches deep with #57 granite. That is 67.5 square feet. 67.5 x 14 / 12 = 78.75 cubic feet, which is 2.92 cubic yards. At 1.40 tons a yard it comes to 4.08 tons, or 4.29 with the 5% ticked. A 4 inch pipe running down the middle displaces only about 0.15 of a cubic yard, so order the full figure and tip the remainder at the outfall.

A garden path, 60 feet by 3 feet, topped with 2 inches of #89 over a base that is already firm. That is 180 square feet. 180 x 2 / 12 = 30 cubic feet, or 1.11 cubic yards, which is 1.56 tons.

Why the ton line moves when the grade does

Volume is fixed by the tape. Weight is not, and the material select is where you tell the tool which figure to use. On this site, #57, #67, #8, #89 and 3/4 inch crushed stone all convert at about 2,800 lb a cubic yard, or 1.40 tons. Screenings and #4 stone come in heavier at roughly 2,900 lb, or 1.45. Crusher run and graded aggregate base run about 3,000 lb, or 1.50, and rip rap is heaviest at around 3,100 lb, or 1.55.

Take the trench above. Those same 2.92 cubic yards are 4.08 tons in #57 and 4.23 tons in screenings, because the fines fill space the clean stone leaves open. Nothing about the trench changed.

Five percent on stone that gets rolled, and the rest of the trench

Angular clean stone settles roughly 5 to 10 percent once traffic works over it, and material with fines is designed to pack down further than that. The 5% box covers ordinary settling and the wheelbarrow that tips on the way across the lawn. It does not replace a compacted depth on engineered work, where the specified thickness is what has to be there after rolling.

Round up after that, especially on a trench. Coming up half a ton short on a drain line means the last few feet go in thin, which is exactly where the water arrives. For loose surface gravel and decorative sizes the gravel calculator is the page to use; for a compacting base course, size it on the crusher run calculator and buy the top stone separately. When the figure looks right, open the product page for the grade you picked, whether that is #57 granite, 3/4" crushed stone, #89 crushed stone or screenings, and set quantity and date there. Delivery is arranged at checkout by ZIP code.

Common questions

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