Aggregate Tonnage Calculator

How does the aggregate tonnage calculator work?

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Enter any two of area, depth, and tons. The calculator solves for the missing value using the material's bulk density. The core formula is area multiplied by depth to get volume, then volume multiplied by density divided by 2,000 to get short (US) tons. If you already know your tonnage and want to find the depth that covers a given area, or the area a tonnage will cover at a given depth, the calculator runs the same formula in reverse. Leave any one of the three fields blank and it fills in the missing value.

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What is the difference between plane area and slope area?

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Plane area is the horizontal "flat" projection of a surface, the same number you would get measuring the footprint on a flat plan sheet or map. Slope area follows the actual inclined 3D surface and accounts for the angle of the grade. On any slope, the slope area is larger than the plane area by a factor that increases with grade. A 3:1 slope has noticeably more surface area than its horizontal footprint suggests. 

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How do I get the area measurement to enter in this calculator?

 

The most accurate source is an earthwork takeoff or a quantity report generated from your project plans. If you receive takeoff reports from QLD, the plane area and slope area for each material section are already in the AGETK report. Those numbers come directly from AGTEK's analysis of your plan geometry. Otherwise, you can take the area from your plan sheets, a scaled drawing, or a measured field dimension. Accuracy on the tonnage output depends entirely on the accuracy of the area input.

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What material densities does this calculator use?

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Preset densities are loose bulk values from Table 30-6 of the Cat Performance Handbook, Edition 48. They represent the weight per unit volume of material in its as-delivered state before compaction. Materials covered include gravel, limestone, sand, sand and gravel mixes, and crushed stone. You can override any preset by selecting Custom and entering a density from your supplier's spec sheet or your material proctor.  Always enter the known density of your material for accurate results.   

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What is AGTEK and how does it connect to aggregate quantity estimates?

 

AgTek is earthwork takeoff and estimating software used by QLD to calculate material quantities from project plans. It analyzes the 2D and 3D plan geometry and produces quantity reports organized by regions and sectional depths, and surface type.

 

Each sectional zone in an AgTek report includes plane area and slope area along with cut, fill, and stripping volumes for the site. For a site with an aggregate placement layer, the report gives you the exact area for that section. That number feeds directly into this calculator. Rather than scaling an area off a drawing and introducing measurement error, you are working from a number derived from the plan geometry itself.

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What is the difference between loose density and compacted density?

 

Loose density is the weight of material per unit volume as delivered from the quarry, before any compaction. Compacted density is higher because the same material occupies less volume after mechanical compaction.

 

A cubic yard of loose crushed stone weighs less than a cubic yard of the same material after a vibratory roller has worked it in. The ratio between the two is the swell factor. This calculator uses loose bulk densities, which matches how suppliers load and ticket material. If your spec calls for a compacted depth, the tonnage you need to order will be higher than what a compacted-density calculation returns. Ask your supplier for their swell factor if you need to reconcile the two.

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Can this calculator solve for area or depth instead of tons?

 

Yes. Leave any one of the three fields blank and the calculator solves for it. Enter tons and depth and it returns the area those tons will cover at that depth. Enter tons and area and it returns the depth. Enter area and depth and it returns the tons required. Only one field can be blank at a time. If all three have values entered, the calculator will prompt you to clear one.

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My material is not in the preset list. What do I enter?

 

Select Custom from the material dropdown and enter the density from your supplier or your material proctor. Be certain you are using the right density weight for the volume selected. 

 

Plant tickets frequently include your material density. For a specialty aggregate, riprap gradation, or anything with a supplier-specific spec, the spec sheet or proctor is the right source. The Cat PHB 48 presets are reference values. Supplier data for your actual material is always more accurate.

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How accurate is this calculator for a real material order?

 

The math is exact given your inputs. The variable is density. Real aggregate density shifts with moisture content, gradation, and source quarry, sometimes by 5 percent or more from reference values.

 

The Cat PHB 48 numbers are standard reference densities, not guarantees for a specific product. On any significant aggregate order, confirm the bulk density with your supplier and build in an overage factor. Five to ten percent is standard practice on aggregate placements depending on your site conditions and the material's compaction behavior. 

 

Does this calculator work for riprap quantities?

 

It will return the tonnage for a given area and depth using riprap's loose bulk density from PHB48 or your own custom value.  Bulk density can vary widely between rip-rap gradations from the same quarry.  Large rip-rap has a significant amount of air space per unit of volume.

 

Riprap design also involves gradation sizing, filter layer design, and slope stability requirements that go beyond a tonnage calculation. Work with your engineer or your state DOT to be certain you are using the right volume and density numbers for your project.