How do you calculate riprap?
Estimate riprap rock volume and mass from sloping protection area, normal layer thickness, toe volume and verified bulk density. Takeoff from a specified revetment section only. No hydraulic stone size, scour depth, slope stability or filter design is selected. Use placed bulk density, not solid-rock density.
Which measurements should you enter?
Measure depth perpendicular to the bank face. A horizontal depth on a sloping bank describes a different layer.
Which equation gives the result?
Sloping face area = bank length × sqrt(horizontal projection² + vertical rise²); rock volume = face area × normal thickness + separate toe volume; mass = volume × matching bulk density
What does a worked example show?
A 20 ft bank with 4 ft horizontal run and 3 ft rise has a 5 ft sloping face and 100 sq ft of face area. A 12 in layer needs 100 cubic feet before toe stone or allowance.
Which assumptions affect the estimate?
Use placed bulk density from the supplier. Solid rock density excludes the voids between stones and can overstate delivered weight.
What should you verify before using the result?
Toe stone is entered as a separate volume. Fabric quantity covers the measured face plus the entered overlap, not an unmeasured toe trench.
How do you keep units consistent?
Select measurement units before entering dimensions. Keep density, price and product coverage units attached to their labels. The calculator converts geometry but does not invent a missing supplier value.
Which input units apply to this worksheet?
The table lists the field units and the condition in which each input is used.
| Input | Units | Condition |
|---|---|---|
| Measured protected surface area | ft² / m² | shape:area |
| Bank / protection length | ft / m | shape:slope |
| Horizontal bank projection | ft / m | shape:slope |
| Bank vertical rise | ft / m | shape:slope |
| Specified rock thickness normal to face | in / cm | all modes |
| Verified placed bulk density (kg/m³) | as labeled | all modes |
| Ordering allowance (%) (optional) | as labeled | all modes |
| Separate toe / apron volume (optional) | as labeled | all modes |
| Verified payload in metric tonnes (optional) | as labeled | all modes |
| Material price per metric tonne (optional) | as labeled | all modes |
| Geotextile area allowance (%) (optional) | as labeled | all modes |
| Geotextile roll coverage (optional) | ft² / m² | all modes |
How can you compare and save scenarios?
Calculate a baseline, add it to comparison and change one project value. Copy or share the result, download the order sheet or print inputs and results. Reload and clear controls return the worksheet to blank numeric inputs.
Which tools help with the next calculation?
Continue with Gravel Calculator and Stone Calculator. Check scope and units before transferring the result.
