Stone calculator for Iowa

Most crushed stone grades convert at about 2,800 lb per cubic yard, which works out to 1.4 tons per yard, and orders are placed by the ton. Use this calculator for all twelve graded products, including 3/8 inch chips and 2.5 inch railroad ballast; it uses the weight assigned to the material selected. A contractor can begin with a specification number, while a homeowner can begin with the work being done. The guide below leads either description to the matching stone.

How the calculation works

1. Because quantity starts with the footprint, measure in feet. For drives and pads, multiply length by width; for drains, multiply trench length by trench width.
2. Set the depth according to the layer's purpose. Use 2 to 3 inches for top courses, 4 inches for bases, and 12 inches or more for French drains.
3. Divide cubic feet by 27 to get cubic yards. Then multiply yards by 1.4 for tons of typical crushed stone.

Product stone weights

Understanding stone size numbers

Numbers identify stone size, with a lower grade number indicating larger pieces. #4 measures 3/4 to 1-1/2 inches. For general drainage, driveways and concrete work, #57 measures 3/16 to 1 inch. #67 is finer, at 1/4 to 3/4 inch, and is often used around pipe. #8 measures about 3/32 to 3/8 inch. #89 includes material from 3/8 inch down to fines, and both grades work in paver joints and finish courses. Screenings contain dust and small chips that form a firm bed for screeding when compacted. Railroad ballast uses angular pieces measuring 1 to 2.5 inches, providing drainage and load support beneath tracks and equipment pads.

Clean stone or fines: choose the right material

Stone products here generally fall into two groups. Clean, washed material such as #57 lets water move through it and is used where drainage is needed. Crusher run, road base, and other mixes containing fines compact into a firm layer for base work. Using the wrong type creates problems: crusher run in a French drain can trap water, while a #57 driveway base can keep moving under traffic. With Iowa's freeze-thaw conditions, drainage matters as much as support beneath a driveway. When plans or permits list a gradation, order the material specified. If the product name is confusing, text the line item to (515) 852-5557; "3/4 clean" and "#57" can refer to the same material under different names.

Common stone order sizes

Example: a 30-foot French drain

At 30 feet long, 12 inches wide and 12 inches deep, a trench contains 30 cubic feet. That comes to 1.1 cubic yards, or 1.6 tons of #57. Although a 4-inch pipe takes up about 0.1 yards through the center, order the full 1.6 tons and put the small amount left over at the outfall. Before placing stone, line the trench with non-woven fabric so Iowa soil does not fill the drainage voids.

Two ways to avoid a wrong stone order

• Use the specification first, then check the alternate name. Crusher run, crush and run, 1 Inch Roadstone, 1 inch minus and road rock can refer to one material. #57 and "57s" refer to the same stone as well.
• Rolling angular stone commonly produces 5 to 10% compaction. Use the calculator's extra-percent setting for ordinary settling, but follow the specified compacted depth on engineered base work.
• Because the base provides support, pavers need compacted stone beneath them. Use screenings or concrete sand only for the thin leveling layer, not dust alone on soft ground.
• Calculate the full trench volume rather than subtracting the pipe. Pipes under 6 inches usually displace less than a wheelbarrow load, so they seldom affect the order.

Crushed stone facts and figures

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