Quantities
Concrete / trench quantity
- where
- net concrete volume (m³)
- length (m)
- width (m)
- depth (m)
- volume to order (m³)
- allowance (%)
Explain this equation
This gives the volume of concrete for a rectangular strip footing or trench fill, and the volume to order with an allowance.
l is the length, b the width and d the depth of the trench, all in metres. V_net is the net volume of concrete in m³. w is the allowance percentage for over-dig and wastage, and V_order is the amount to order.
Volume is length times width times depth. Multiplying by (1 + w/100) adds the allowance.
A 10 m trench 600 mm wide and 300 mm deep holds 1.8 m³. With 5% allowance, order 1.89 m³. Doubling the depth doubles the concrete.
Watch out: trenches are rarely perfect. Measure the actual dig; this does not design the foundation.
Calculate volume for a rectangular strip and an ordering allowance.
Enter your values to see the result.
Good to know
All dimensions in metres. Measure excavation variations; this does not design foundation width, depth, reinforcement or bearing capacity.
Sources
- Geometry / arithmetic
Estimates are not design approval or British Standards compliance checks. Structural arch, retaining-wall, wind, foundation, lintel and masonry-capacity design are not performed. Use the project engineer’s specification.