Rectangular slab concrete calculator

Calculate a simple slab volume in cubic yards and cubic meters.

Direct answer

Multiply length by width by thickness in consistent units. Treat thickened edges, footings, beams, piers, steps, and field allowance as separate volumes.

Interactive tool

Enter your measurements

Enter valid measurements and select Calculate.

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Formula

Volume = length x width x thickness. Imperial cubic yards = cubic feet / 27.

Worked example

A 24 ft by 30 ft slab at 4 in is 240 cubic feet or 8.89 cubic yards before allowance; 5% gives about 9.33 cubic yards.

Assumptions

The slab is a rectangular prism of uniform thickness.
The allowance is shown separately from raw geometric volume.
No overlapping shapes are included.

Caveats

The tool does not select thickness, mix, reinforcement, joints, subbase, or footing geometry.
Excavation, forms, grade, weather, access, and supplier ordering affect actual need.
Foundation design and local approval are required.

Primary references

2024 International Residential Code: FoundationsInternational Code Council; accessed 2026-08-02.
Guide for the Use of the International System of Units (SI)National Institute of Standards and Technology; accessed 2026-08-02.

Understand and continue

Concrete volume from explicit geometry

Calculate rectangular planning volumes while naming excavation, reinforcement, thickening, and field variation as separate work.

Read supporting guide

Garden shed concept

A small storage shell with a wide door, central retrieval aisle, and wall-mounted storage zones.

Open starting concept

Planning quantity, not construction directionThis calculator does not verify codes, specifications, structure, utilities, product suitability, purchasing, pricing, installation, or safety. Verify the result and all project decisions with qualified local professionals.