Quick answer: A 12 × 12 ft patio at 4 in thick is about 1.78 yd³ raw volume. With a 10% planning allowance, that is about 2.0 yd³.
The basic calculation
Multiply length × width × thickness to get cubic feet, then divide by 27 to convert to cubic yards. For a 12 × 12 ft slab at 4 inches thick: 12 × 12 × (4/12) ÷ 27 ≈ 1.78 yd³.
Why the order may be higher
A planning allowance can help cover small measurement differences, uneven subgrade and handling loss. It does not replace a site-specific order quantity. Thickened edges, footings and non-rectangular shapes must be added separately.
Before calling a supplier
- Confirm finished dimensions and thickness.
- Ask whether the supplier has a minimum load or short-load fee.
- Confirm mix specification and access for the truck.