Area Calculator
Calculate area in square metres for rectangles, triangles, circles, walls, and rooms. Subtract windows and doors to get the net area for painting, tiling, or insulation.
Concrete Calculator
Quickly calculate how much concrete you need for a slab, footing, column, or round post. Enter dimensions, set quantity and waste margin — get the result in m³ and litres instantly.
Enter dimensions to see the concrete volume needed.
Total Concrete Needed
Net Volume
Tips
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Always add 5-10% waste margin to account for spillage, uneven ground, and formwork variations.
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It is better to have slightly too much concrete than too little — a short pour can compromise structural integrity.
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Standard ready-mix concrete is typically delivered in full or half cubic metre increments. Round up when ordering.
Results are informational. Calculation is based on your input and public rules, official accounting may differ. For accuracy, confirm the final result if needed from the appropriate official source or specialist.
How it works?
How to calculate concrete volume
Enter dimensions in metres and the calculator shows the required concrete volume instantly in m³ and litres. The result updates live as you type.
Concrete volume formulas in m³
Slab / Footing: Length × Width × Depth. Use for driveways, patios, garage floors, strip footings, and foundation pads.
Column: Width × Depth × Height. For rectangular or square structural columns and pillars.
Round Post (Cylinder): π × (Diameter ÷ 2)² × Height. For sonotubes, round piers, and cylindrical posts.
How much concrete for a slab or footing
The formula is the same: length times width times depth. For example, 5 × 3 × 0.1 metres = 1.5 m³ of concrete. Footings are typically narrower but deeper — for example, 10 × 0.6 × 0.3 m = 1.8 m³.
Concrete volume for columns and round posts
For columns, multiply width, depth, and height. For round posts, the calculator uses the cylinder formula: π × (diameter ÷ 2)² × height. Set the quantity if you are pouring multiple identical elements.
Always add a waste margin (5% or 10%) to cover spillage, uneven surfaces, and formwork tolerances. The adjusted total is what you should order.
Frequently asked questions
How do I calculate how much concrete I need?
Measure the length, width, and depth in metres and multiply them together. For example, 5 × 3 × 0.1 m = 1.5 m³. This calculator does the math for you — just enter dimensions and the result appears instantly.
How many litres is 1 m³ of concrete?
1 cubic metre equals 1,000 litres. The calculator shows results in both m³ and litres, making it easy to compare with different packaging sizes.
Should I add extra margin when ordering concrete?
Yes, always. We recommend adding 5-10% waste margin. Uneven ground, formwork tolerances, and spillage mean actual usage is always slightly more than the calculated volume. A short pour is far more costly than ordering a little extra.
Does this calculator work for footings and columns too?
Yes. Select the matching tab — Slab / Footing uses length × width × depth, Column uses width × depth × height, and Round Post calculates cylinder volume from diameter and height.
How many bags of concrete do I need instead of ready-mix?
A standard 25 kg bag of pre-mixed concrete yields roughly 0.012 m³. Divide the total volume by 0.012 to get the approximate bag count. For anything over about 0.5 m³, ready-mix delivery is usually more practical and cost-effective.