How many cubic yards are in a square foot?

A square foot alone is an area, not a volume, so there's no fixed conversion until you add a depth. Multiply your area in square feet by the depth in feet, then divide by 27 to get cubic yards. For example, 100 sq ft at 0.5 ft deep = 50 ft³ ÷ 27 ≈ 1.85 cubic yards.

How do I convert square feet to cubic yards for concrete?

Multiply the slab area in square feet by the slab thickness in feet to get cubic feet, then divide by 27. A 10 ft x 10 ft slab (100 sq ft) at 4 in (0.33 ft) thick needs 100 x 0.33 = 33 ft³, which is 33 / 27 ≈ 1.22 cubic yards before waste.

Does this calculator work for gravel and mulch as well as concrete?

Yes — the area x depth calculation and waste allowance apply the same way whether you're pouring concrete, spreading gravel or laying mulch. Just adjust the material price field to match what you're actually buying.

Square Feet to Cubic Yards Calculator — Concrete Volume Conversion | Gibraltar

Square Feet to Cubic Yards Calculator

Concrete, mulch and gravel are priced and delivered by the cubic yard, but you almost always start with a flat area in square feet and a depth in inches. This calculator does that conversion in one step: enter your area (or a length and width instead) plus the depth you're filling or pouring, and it multiplies the two to give you cubic yards — plus a waste-adjusted purchase volume and a material cost estimate.

How to Use This Calculator

Enter the length and width of the area, or switch to a single area figure if you already have square feet.
Enter the depth of the slab, fill or mulch layer, in inches or feet.
Set a waste allowance — 10% is the default, covering compaction and sub-grade irregularity.
Read off the volume, the waste-adjusted purchase volume to order, and the estimated material cost.

The Math Behind the Conversion

The formula is simple: volume = area x depth, with depth converted into the same linear unit as the area before multiplying, then divided by 27 to turn cubic feet into cubic yards (since 1 yd³ = 3 ft x 3 ft x 3 ft = 27 ft³). Worked example, this calculator's own default: a 9 ft x 6 ft area (54 sq ft) at a 0.5 ft (6 in) depth. Volume = 54 x 0.5 = 27 ft³, and 27 / 27 = 1 cubic yard exactly. Add a 10% waste allowance and you'd order 1.1 cubic yards.

Pro Tips

At around £177 per m³ (ready-mix concrete, delivered), the calculator's own default example (0.841 m³ incl. 10% waste) works out to roughly £149 in material. Ready-mix concrete in Gibraltar is typically imported or shipped in from Spain, so pricing depends heavily on delivery logistics — check this against a current supplier quote before ordering a large pour.

Depth is the field most often entered in the wrong unit — double-check inches vs. feet, since a slab poured 6 in deep is 0.5 ft, not 6 ft.
Ready-mix concrete is typically sold in quarter-yard increments with a minimum load — round your purchase volume up to that increment rather than down.