Enter your measurements
Select your project shape, input your dimensions, and click calculate to see exactly how much concrete you need.
Estimation of concrete volume for standard construction slabs and footings
Practical Example
Imagine you are pouring a driveway slab that is 5 meters long, 3 meters wide, and 100 mm deep.
- • Convert depth to meters: 100 mm = 0.1 m
- • Base Volume: 5m × 3m × 0.1m = 1.5 m³
- • Add 10% Waste Factor: 1.5 m³ × 1.10 = 1.65 m³
You would order 1.7 m³ from a ready-mix supplier or manually mix approximately 165 bags of 20kg premix concrete.
Formula / Calculation Method
Rectangular Slabs
For square or rectangular pours, multiply the three dimensions together (ensuring all are in the same unit):
Cylindrical Posts
For round holes or tubes, find the area of the circular base and multiply by depth:
Common Mistakes
Ignoring the waste factor
Always add 5-10% to account for uneven subgrades, formwork bowing, and spillage. Ordering exactly the calculated amount almost guarantees you will run short.
Mixing up measurement units
Entering a 100mm depth as "100" in a formula expecting meters will result in an order 1,000 times larger than necessary.
Using the concrete estimate responsibly
The calculator estimates geometric concrete volume for rectangular slabs and footings or cylindrical post holes and columns. Enter finished internal form dimensions, keep every input in the displayed unit, and use the waste percentage only as an allowance for site variation—not as a substitute for measuring irregular excavation or checking formwork.
Inputs and outputs
- Length, width and thickness define rectangular volume.
- Diameter, depth or height and quantity define cylindrical volume.
- Waste is applied after base volume: total = base volume × (1 + waste ÷ 100).
- Metric results are cubic metres; imperial results are cubic yards. Bag, sand, stone and water figures are planning approximations tied to the selected preset.
Verified worked example
A 4 m × 3 m slab that is 100 mm thick has a base volume of 4 × 3 × 0.100 = 1.20 m³. With 10% waste, 1.20 × 1.10 = 1.32 m³. The calculator returns 1.32 m³ for those inputs.
Assumptions, ordering and safety
Real pours can require more or less material because subgrade levels, trenches, penetrations, form movement and supplier batch tolerances differ. The site-mix and premix-bag outputs are rough yield estimates; they do not design concrete strength or replace the manufacturer’s stated bag yield, a supplier quotation, a project specification or an engineered mix design. Confirm structural dimensions, reinforcement, strength class, joints and curing requirements with the responsible designer or contractor before ordering.
Wet cement can cause serious skin and eye injury, and cutting or grinding cured concrete can create respirable crystalline silica. Follow the product safety data sheet and applicable workplace controls, and use suitable gloves, boots, eye protection and dust controls.
References
- Federal Highway Administration: SI conversion table — cubic-foot and cubic-yard volume conversions.
- OSHA: Concrete and Concrete Products — cement, wet-concrete and silica hazard resources.