How much concrete do I need for a garage floor?

A garage floor is usually a simple slab, but the area is larger and the waste factor can matter more if access is tight.

Best for

Worked example

A 6 m by 5 m garage floor at 0.12 m thickness

Large rectangular slabs are straightforward, but rounding up a little is still sensible for edge losses and finish work.

Example

6 m × 5 m × 0.12 m = 3.6 m3. With 8 percent waste, the adjusted order volume is 3.89 m3.

Formula

Volume = length × width × thickness

Adjusted volume = volume × (1 + waste / 100)

Planning notes

Garage slabs often need extra material at the perimeter and around door thresholds.

Use the design depth you intend to pour, not a nominal finish thickness.

A small waste factor helps cover uneven subbase and site losses.

Use the slab page for generic rectangular slabs.

Switch to a patio page for a smaller slab use case.

Open the main calculator for custom dimensions.