Work out cross section area instantly with clear inputs, formula shown and shareable results.
A two-level cross-section on flat ground is a trapezium: the rectangle of formation width times depth, plus two triangles whose combined area is the side slope ratio times the depth squared. Because the slope term is squared, side slopes dominate the volume on deep cuttings and embankments.
Trapezoidal section area
A = b h + s h², where s is the horizontal run per unit of vertical rise
Top width
Top width = b + 2 s h
A = b h + s h², where s is the horizontal run per unit of vertical rise. A two-level cross-section on flat ground is a trapezium: the rectangle of formation width times depth, plus two triangles whose combined area is the side slope ratio times the depth squared.
Then it becomes a three-level section and the two side areas differ. The section must be computed from the actual ground levels at each offset rather than from a symmetrical formula.
This calculator takes 3 inputs: Formation width, Depth of cut or height of fill, Side slope, horizontal to one vertical. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.