Riprap Layer Volume and Tonnage
Cubic yards and tons of stone to order for a riprap layer.
Example
You enter
- Plan area of the riprap layer (ft²) 500
- Layer thickness (ft, at least 1.5 x D50) 2
- Stone unit weight (pcf) 165
You get
- Layer volume 37.0 cy
- Stone to order 82.5 tons
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scopevolume = area x thickness / 27, tons = area x thickness x unit weight / 2000. A 500 sf outlet apron 2 ft thick is 37 cy and 82.5 tons at solid 165 pcf, but ordering to a placed 130 pcf (voids counted) drops it to 65 tons. The order-quantity companion to riprap-d50.
Formula or tablevolume_cy = area_sf x thickness_ft / 27; tons = area_sf x thickness_ft x unit_wt_pcf / 2000.
Source and editionLayer take-off identity by name (plan area x thickness x unit weight); first-principles volume arithmetic.
Free accessThe layer take-off is public quantity-survey geometry; the unit weight comes from the stone source.
What governsEstimate. AHJ and licensed professional govern.
API field namesarea_sf, thickness_ft, unit_wt_pcf, volume_cy, tons
- Unit weight 165 pcf solid-rock default; order to a placed 120-135 pcf (voids counted)materials practice
- Layer thickness at least 1.5 x D50 (from riprap-d50); the plan sets itUSACE riprap practice