River Rock Calculator

Quick answer#

River rock and river stone are often sold by the cubic yard, ton or bag. This calculator keeps those units connected through an editable bulk density and shows the effect of any ordering allowance separately.

The live result shows both volume and mass because suppliers may quote either. Every density preset is editable; it is not a promise that locally supplied material has that unit weight.

Formula and calculation method#

For circular beds, enter the full diameter. For curved or irregular landscapes, use a measured area. The large- and small-stone density options are sensitivity checks only; supplier data should replace them.

The shared calculation path is:

1. Determine measured volume in cubic metres internally.
2. Calculate base mass as volume × bulk density.
3. Calculate order quantity as base quantity × (1 + order allowance ÷ 100).
4. Divide order mass by entered bag or load capacity and round up to whole units.
5. Apply optional pricing only from the price, fixed delivery cost and tax entered by the user.

One cubic yard is exactly 27 cubic feet. One US short ton is exactly 2,000 pounds. Metric mode reports cubic metres and metric tonnes.

Worked example#

A 15 ft × 6 ft bed at 3 in deep contains about 0.833 yd³. At 105 lb/ft³, the base mass is about 1.181 short tons. A 5% allowance produces about 0.875 yd³ and 1.24 short tons.

The example is reproducible in the calculator, but a purchase decision should use measurements and density for the actual project and product.

Choosing a density#

Bulk density is mass per occupied bulk volume, including the spaces between particles. It is not the same as the solid-rock particle density. Moisture, gradation, particle shape, source and test procedure can all affect it.

The planning presets are intentionally editable sensitivity values. Prefer, in order:

1. A density or tons-per-yard figure for the exact supplier product.
2. Project test or specification data representing the required material condition.
3. An explicitly labelled planning value that is later replaced before ordering.

ASTM C29/C29M describes a standardized method for determining aggregate bulk density (unit weight) and voids. The calculator does not claim that its editable presets are laboratory results under that standard.

Order allowance, bags and loads#

The order allowance is shown separately and applied once. Do not use it to duplicate waste, settlement or compaction already built into a supplier recommendation or project quantity.

Bag and load counts use the capacities entered and round upward. They are planning divisions only. Confirm package weight, supplier minimums, legal payload, axle limits, access and split-delivery requirements independently.

Assumptions and limitations#

The calculator does not design drainage, erosion control or load-bearing layers. It does not account for void filling, fabric, edging, rock migration or an uneven subgrade unless reflected in the entered measurements.

Cost is optional and uses only the entered rate per short ton or metric tonne, fixed delivery cost and tax. Currency selection changes the label but does not perform exchange-rate conversion. Results are estimates, not bids, engineering designs, specifications or guarantees of availability.

Sources and methodology#

• NIST: SI Units — Volume — definition of volume and the cubic metre as the SI derived unit.
• NIST: SI Units — Mass — mass and SI-unit reference.
• NIST SP 811 conversion factors — U.S. customary and SI conversion basis.
• ASTM C29/C29M — standard test method for aggregate bulk density (unit weight) and voids.
• Vulcan Materials aggregate tonnage estimator — industry example showing aggregate estimates depend on entered dimensions and density.

Sources identify the measurement and density methodology. They do not certify a specific material preset, local product or project design.