Concrete Volume Calculator
Use this concrete volume calculator to estimate how much concrete you need for common pours such as slabs, footings, pads, and columns. The calculator works out the concrete volume from the dimensions you enter and can help with early planning before you move on to bag counts, ready-mix ordering, or cost checks. It is designed as a practical quantity tool for construction and DIY projects.
Recommended: 10% for standard conditions
How this calculator works
This calculator calculates concrete volume by applying the correct geometric formula for the selected shape. For rectangular pours such as slabs, footings, and walls, the volume is length × width × depth (or height for walls). For circular or cylindrical shapes — circular slabs and columns — the volume uses the circular cross-section area multiplied by the depth or height. All inputs are in the same unit (metres for metric, feet for imperial) and the result is shown in m³, ft³, and yd³. A waste factor is applied to the base volume, and a bag estimate is shown using the selected bag size and its yield.
Formulas used
volume = length × width × thickness
volume = length × width × depth
volume = length × height × thickness
radius = diameter / 2
volume = π × radius² × thickness
radius = diameter / 2
volume = π × radius² × height
total volume = base volume × (1 + waste % / 100)
bags = ⌈total volume ÷ yield per bag⌉
Bag yield scales with bag weight: 20 kg ≈ 0.01 m³, 25 kg ≈ 0.0125 m³, 30 kg ≈ 0.015 m³, 40 kg ≈ 0.02 m³. The exact formula depends on the shape selected. The visible formulas match the shapes supported by the live tool.
Worked example
For a rectangular concrete slab measuring 4 m long, 3 m wide, and 0.1 m thick, the base volume is 4 × 3 × 0.1 = 1.2 m³. With a 10% waste allowance applied, the total volume becomes 1.2 × 1.10 = 1.32 m³. The results card also shows this in ft³ and yd³, and shows a bag estimate based on the selected bag size and its yield.
Why concrete volume matters
Concrete volume is the starting point for almost every other material estimate. Once the volume is known, you can convert it into bags, ready-mix order quantities, rough cost, or slab weight depending on the job. That makes a volume calculator useful not just for slabs, but for many other simple concrete shapes as well.
Frequently asked questions
Related tools
- Concrete Footing Calculator — volume, bags and cost for strip footings, pads and post holes
- Concrete Slab Bag Calculator — how many bags of concrete for a slab
- Dry Pour Concrete Calculator — volume, bags and cost for dry-pour slabs
- Weight of Concrete Slab Calculator — estimate slab weight in kg, tonnes and lb
- Screed Calculator — sand & cement or liquid screed quantities for the floor finish above your slab
- Mortar Calculator — sand and cement for brickwork and blockwork above the foundation
Guides worth reading
- How much concrete do I need? Full UK guide — grades, wastage, worked example and short-load traps
- Concrete Mix Ratio UK — GEN1 to C25, ratios by job and how site mixes map to BS 8500 grades
Disclaimer: This calculator is for planning and estimating only. Actual concrete quantities vary with shape, dimensions, waste, and site conditions. Always check final project requirements before ordering.