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Concrete Calculator

Estimate concrete for slabs, columns, tubes, solid stairs or curb-and-gutter sections, with mixed units, allowance and volume-based pricing.

Your inputs

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EXAMPLE RESULTCalculated locally
Net concrete
2.47 yd³
With allowance
2.72 yd³
With allowance, metric
2.08 m³
Clear inputs. Transparent methods.
My workspace

Calculate with your inputs to save a result or compare scenarios.

How it works

A useful distinction

Thickness errors affect the entire slab

For a fixed slab footprint, increasing thickness from 4 to 5 inches raises net concrete volume by 25%. Check depth measurements before adjusting the allowance; an extra percentage cannot reliably correct an incorrectly specified slab thickness.

Separating concrete volume from an order quantity

Select the shape that matches the slab, column, footing, or stairs, and check each thickness and depth unit carefully. The geometric volume describes the idealized form. Use the supported quantity and cost inputs to explore an allowance or price, while keeping those assumptions explicit. Site irregularities and supplier ordering increments can make the delivered amount differ from the geometric estimate.

Slab or rectangular footing: formula and assumptions

Cubic yards = length(ft)×width(ft)×thickness(in)/12/27.

Volume does not account for reinforcement displacement or construction tolerances beyond your allowance.

Round column: formula and assumptions

Volume = πr²×height×quantity.

Convert all dimensions to feet before calculating cubic yards.

Hollow round column: formula and assumptions

Volume = π(outer radius²−inner radius²)×height×quantity.

Inner diameter must be smaller than outer diameter.

Solid stairs to ground: formula and assumptions

Volume = width×riser×[tread run×N(N−1)/2 + platform depth×N].

This assumes a solid stair block to ground, N risers, N−1 regular treads, and a top platform at full height.

Mixed-unit shapes, quantity & cost: formula and assumptions

Curb cross-section = (curb width + exposed gutter width) × flag thickness + curb width × height above flag.

Each shape uses independently converted dimensions. Quantity is applied once. Solid stairs include a full-height top platform. Net and ordered volume are displayed separately.

Worked example

Using the Slab or rectangular footing example:

Inputs
Length (ft)
20
Width (ft)
10
Thickness (inches)
4
Extra allowance (%)
10
Method

Cubic yards = length(ft)×width(ft)×thickness(in)/12/27.

Result

Example result

Net concrete: 2.47 yd³

With allowance: 2.72 yd³

With allowance, metric: 2.08 m³

These are illustrative inputs. Change the values to explore a different scenario.

Formula references

References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.

Common questions

How does net concrete volume differ from ordered volume?

Net volume comes from the geometry and quantity. Ordered volume adds the entered allowance; pricing can use either selected basis.

What does the curb-and-gutter section include?

It combines the flag slab under curb and exposed gutter with the curb height above that slab, avoiding an overlapping volume.

What shape does the stair-volume mode assume?

A solid block to ground with N risers, N − 1 regular treads and a top platform at full height.

Prepared by Finflo. See our methodology and editorial policy.