Crushed Rock Calculator

Heavy crushed rock, surge stone, and rip-rap are coarse quarry materials sized from 3 inches to over 18 inches in diameter, engineered primarily for d

Construction

Embankment / Trench Surface Area

sq ft

Surface area of rip-rap or rock protection zone in square feet

Heavy Crushed Rock Grade

Rock Layer Thickness

Layer depth in inches (must be at least 1.5× the maximum stone size)

Rock Bulk Density

lb/cu yd

Bulk density in truck bed (USACE standard for broken rock: 2,400-2,600 lb/cu yd)

Over-Excavation & Void Allowance

Inter-rock void variance and uneven embankment subgrade buffer (10-15% standard)

Formula & Methodology

Converted Depth (ft) = Rock Layer Depth (in) ÷ 12 Volume (cu yd) = [Area (sq ft) × Converted Depth (ft)] ÷ 27 Gross Volume = Volume (cu yd) × (1 + Waste % ÷ 100) Crushed Rock to Order (US tons) = [Gross Volume (cu yd) × Density (lb/cu yd)] ÷ 2,000

Because large crushed rock has substantial void spaces between irregular boulders, US Army Corps of Engineers (USACE) engineering guidelines stipulate that rip-rap layers must be placed at a depth equal to at least 1.5 times the median rock diameter (D50). Weight is calculated from volume and bulk density (typically 2,400 to 2,600 lb/cu yd in transit trucks). Tonnage is rounded strictly up to prevent erosion failure.

Crushed Rock to Order

3.97 US tons

Overview

Heavy crushed rock, surge stone, and rip-rap are coarse quarry materials sized from 3 inches to over 18 inches in diameter, engineered primarily for drainage ditch armoring, culvert erosion control, shoreline stabilization, and heavy logging road sub-bases. This Crushed Rock Calculator determines required weight-based tonnages for large rip-rap stones, incorporating layer thickness checks and inter-rock void ratios.

Estimates are for material planning and budgeting purposes only. This calculator does not provide geotechnical engineering, structural design, or official building code compliance advice. Always verify measurements, aggregate densities, and compaction requirements with a local quarry supplier or licensed contractor before ordering materials or commencing construction.

Worked Examples

Example 1: Drainage Ditch Armoring with 3"-6" Surge Stone (150 sq ft at 6 in Deep)

Inputs: Area = 150 sq ft, Grade = 3"-6" Surge, Depth = 6 in, Density = 2,550 lb/cu yd, Waste = 12%

Convert depth: 6 in ÷ 12 = 0.50 ft.
Net cubic feet: 150 sq ft × 0.50 ft = 75.00 cu ft.
Convert to cubic yards: 75.00 ÷ 27 = 2.7778 cu yd.
Add 12% void and slope waste factor: 2.7778 × 1.12 = 3.1111 cu yd.
Calculate total weight: 3.1111 cu yd × 2,550 lb/cu yd = 7,933.33 lb.
Convert to US tons: 7,933.33 ÷ 2,000 = 3.97 US tons (3.60 metric tonnes).

Final Answer: 3.97 US tons to order (3.11 cu yd; 3.60 metric tonnes)

Example 2: Culvert Outfall with 6"-12" Class 1 Rip-Rap (12 in Deep)

Inputs: Area = 200 sq ft, Grade = 6"-12" Class 1, Depth = 12 in (1.0 ft), Density = 2,550 lb/cu yd, Waste = 15%

Convert depth: 12 in ÷ 12 = 1.0 ft.
Net volume: 200 sq ft × 1.0 ft = 200.00 cu ft ÷ 27 = 7.4074 cu yd.
Add 15% placement waste: 7.4074 × 1.15 = 8.5185 cu yd.
Calculate weight: 8.5185 cu yd × 2,550 lb/cu yd = 21,722.22 lb.
Convert to tons: 21,722.22 ÷ 2,000 = 10.86 US tons.

Final Answer: 10.86 US tons to order (8.52 cu yd; 10.86 tons ordered)

Example 3: Shoreline Embankment with 12"-18" Heavy Rip-Rap (18 in Deep)

Inputs: Area = 400 sq ft, Grade = 12"-18" Class 2, Depth = 18 in (1.5 ft), Density = 2,500 lb/cu yd, Waste = 15%

Convert depth: 18 in ÷ 12 = 1.50 ft.
Volume: 400 × 1.50 = 600.00 cu ft ÷ 27 = 22.2222 cu yd.
Gross volume (15% waste): 22.2222 × 1.15 = 25.5556 cu yd.
Weight: 25.5556 × 2,500 ÷ 2,000 = 31.94 US tons.

Final Answer: 31.94 US tons to order (25.56 cu yd; approx. 2 truckloads)

How to Use This Calculator

Enter the embankment, ditch, or shoreline surface area requiring rock armoring in square feet.

Select the rock size grade based on water flow velocity and slope angle.

Enter the rock layer placement depth (verify it is at least 1.5 times the median rock size).

Review the bulk density (default: 2,550 lb/cu yd per USACE EM 1110-2-2302 standards).

Check the calculated tonnage to order and ensure heavy non-woven geotextile cushion fabric is planned beneath the stone.

Reference Table

Rock Grade	Median Stone Size	Min Layer Depth	Weight per 100 sq ft	Typical Water Velocity
Shot Rock / Surge	3" to 6"	6 in (0.5 ft)	2.64 tons	Under 5 ft/second
Class 1 Rip-Rap	6" to 12"	12 in (1.0 ft)	5.28 tons	5 to 10 ft/second
Class 2 Rip-Rap	12" to 18"	18 in (1.5 ft)	7.92 tons	10 to 14 ft/second
Class 3 Heavy Rip-Rap	18" to 24"	24 in (2.0 ft)	10.56 tons	Over 14 ft/second
Gabion Stone	4" to 8"	12 in (1.0 ft)	5.10 tons	Wire basket retained

Frequently Asked Questions

What is the difference between crushed stone and crushed rock/rip-rap?

Crushed stone refers to smaller aggregate screened under 2 inches (such as #57 3/4-inch stone) used for driveways and concrete. Crushed rock (or rip-rap) refers to heavy, coarse stone pieces ranging from 4 inches to over 24 inches in diameter engineered for high-velocity erosion protection.

Why must heavy rip-rap be placed on a geotextile cushion fabric?

Without heavy non-woven geotextile filter fabric, flowing groundwater will wash fine underlying soil out through the large void spaces between rip-rap boulders, causing the embankment to collapse and undermining the rock barrier.

How thick should a rip-rap erosion protection layer be?

Civil engineering standards mandate that the layer thickness must be at least 1.5 times the spherical diameter of the median rock size (D50), or equal to the maximum rock diameter, whichever is greater, to prevent water from penetrating through to the bare soil.

Can heavy rip-rap rock be dumped directly onto bare soil?

No. Rip-rap dumped directly on soil will sink into the mud under its own weight. A 4-inch bedding layer of #57 crushed stone or heavy non-woven filter fabric must be installed first to distribute point loads.

How is heavy rip-rap delivered to a job site?

Because individual rip-rap stones can weigh between 25 and 200 pounds each, they are hauled in heavy-duty steel-body dump trucks. Stones larger than 12 inches typically require an excavator with a thumb attachment to place properly without rolling.