At 4 inches thick, a 12×12 slab requires about 1.78 theoretical cubic yards. With a 10% waste allowance, the planning amount is roughly 1.96 cubic yards.
Measure inside the forms
Use the actual finished dimensions rather than relying on a rough project name such as “12×12.”
Choose thickness for the project
Patio, shed, equipment and vehicle slabs can have different design requirements. Verify the design before ordering concrete.
Add waste deliberately
Waste helps cover normal variation such as uneven subgrade and small placement losses. It should not replace accurate measurement.
Run several scenarios
Change thickness and waste percentage in the Concrete Calculator before asking suppliers for delivery quotes.
Run your own numbers: Calculate the slab in the Concrete Calculator.