Concrete Slab Calculator
Quickly estimate the amount of concrete needed for your slab project. Get accurate volume and cost estimates for cement, sand, and gravel.
Measurement System
Switch units without changing the underlying calculation.
Input Dimensions
Calculation Results
Planning estimate only
Results are based on the values and assumptions entered here. Confirm quantities with current product information and suppliers; use qualified local professionals for structural, safety-critical, permitted, or code-regulated work.
Read the calculator terms and limits →How to Use the Concrete Slab Calculator
Using our concrete slab calculator is straightforward and designed to save you time on the job site. First, measure the length and width of the area where you plan to pour the concrete. Next, determine the required thickness of the slab—standard residential slabs are usually 100mm to 150mm (4 to 6 inches) thick depending on the intended load.
Enter these values into the input fields above. If you know the local price of concrete, you can also enter the cost per unit to get a real-time price estimate. Once you click "Calculate Now," the tool will instantly provide the total volume in cubic meters, the estimated number of cement bags required, and the projected total cost. This precision helps you order exactly what you need, minimizing expensive waste and environmental impact.
Pro Tips for a Better Concrete Slab
Use these practical checks alongside the concrete slab calculator to reduce ordering errors and prepare for a smoother pour. Project specifications and local requirements always take priority for structural or load-bearing work.
Convert Thickness Before Calculating
Enter consistent units. If you measure the slab in metres, convert millimetres first: 100mm is 0.1m and 150mm is 0.15m. A small conversion error can materially change your concrete volume estimate.
Check Depth at Several Points
Use stakes, a string line, or a laser level to check the prepared depth across the entire area—not only at the edges. Uneven excavation is a common reason actual concrete use exceeds the calculated volume.
Prepare the Base Before Delivery
Complete compaction, forms, drainage, reinforcement, access, and tools before the concrete arrives. A stable prepared base supports the specified slab thickness and prevents last-minute delays during the pour.
Plan Joints and Curing Early
Mark control-joint locations before placing concrete, then protect the fresh slab from rapid drying as required by the job specification. Good joint layout and curing help manage shrinkage-related cracking.
Concrete Slab Calculator FAQs
How do I calculate concrete volume for a slab?
Multiply the slab length by its width and thickness using the same unit. For metric measurements, convert thickness to metres first: a 10m by 5m slab at 100mm (0.1m) thick needs 5 cubic metres of concrete before allowing for site conditions.
How much extra concrete should I order?
Allow for small variations in excavation, compaction, formwork, and spillage. A modest 5% to 10% ordering allowance is common for many projects, but confirm delivery increments and the final quantity with your ready-mix supplier.
What concrete slab thickness do I need?
The required slab thickness depends on its use, ground conditions, reinforcement, and local requirements. Light-duty patios are commonly thinner than slabs carrying vehicles or structural loads. Confirm the specification with local code requirements or a qualified professional before ordering concrete.
Can I pour concrete directly on soil?
Do not treat loose or organic soil as a finished base. Remove unsuitable material, prepare and compact an appropriate sub-base, and follow the project specification for drainage and any moisture barrier before the concrete pour.
When should control joints be planned for a concrete slab?
Plan control-joint locations before the truck arrives. Joints guide shrinkage cracking into deliberate lines and should be placed and cut in accordance with the slab design, concrete mix, weather, and finishing schedule.