Civil Engineering

Concrete Volume Calculator

Estimate concrete volume for slabs, footings, pads, and other rectangular placements.

Engineering schematic

Slab dimensions

Static symbolic figure. Enter project values in the calculator fields below.

Axonometric rectangular concrete slab with length L, width W, thickness t, volume V equals L W t, and a separate waste-factor note. — Symbols
L
slab length
W
slab width
t
uniform slab thickness
V
base concrete volume

Result

4.89 yd3 (3.74 m3) recommended order quantity

Base volume

120

Waste factor

10%

Cubic feet

132

Cubic yards

4.89

Cubic meters

3.74

Step-by-step calculation

Convert thickness
$t=0.5$
Calculate base volume
$V=20\times12\times0.5=120$
Apply waste allowance
$V_{\mathrm{order}}=120\left(1+\frac{10}{100}\right)=132$

What this means

Use this as a preliminary quantity estimate and confirm ordering increments with the ready-mix supplier.

Assumptions

Rectangular slab or prism
Uniform thickness
Waste factor covers minor over-excavation and finishing loss

Formula Used

V=LWT

Step-by-Step Example

A 20 ft by 12 ft slab with 6 in thickness and 10% waste needs about 4.89 cubic yards.

Engineering Notes

Check units, assumptions, boundary conditions, groundwater, drainage, and whether the simplified method is appropriate before using a result in any project decision.

FAQ

Should I include waste?

Yes. Small jobs commonly use 5% to 10%; irregular excavations may need more.

Does this replace supplier takeoff?

No. Confirm delivery increments and site access with your supplier.