Concrete Volume Required
0 m³
Including waste allowance
Calculate concrete volume for slabs, footings and pads in cubic metres, cubic feet and bags
Calculate the exact volume of concrete needed for your slab project instantly. Supports metric and imperial inputs, outputs cubic metres, cubic feet, litres, and number of premix bags. Includes formula, reference tables, and real-world project examples for 2026.
Professional concrete volume estimation for residential, commercial and civil construction projects
Calculate the volume of a concrete slab using the simple formula: Volume = Length × Width × Thickness. Enter your slab dimensions in metres or feet and get the volume instantly in cubic metres (m³), cubic feet (ft³), litres, and the number of 20 kg or 25 kg premix bags required. A 10% waste allowance option is also included for realistic ordering estimates in 2026.
Switch seamlessly between metric (metres and millimetres) and imperial (feet and inches) input modes. Whether your architect provided plans in millimetres, your builder quoted in feet, or you are reading an older set of drawings that mix both systems, our calculator handles all common input units and outputs results in both metric and imperial volume units simultaneously.
Essential for builders, concreters, DIY homeowners, civil engineers, and project managers in 2026. Knowing the exact concrete volume prevents costly over-ordering or disruptive under-ordering. The calculator covers house slabs, garage floors, driveways, pathways, footings, post footings, and any rectangular or square concrete pour requiring accurate material estimation before ordering from a ready-mix supplier.
Enter your slab dimensions below to calculate the concrete volume needed
A concrete slab is a flat, horizontal structural element cast from concrete — a mixture of cement, sand, aggregate, and water — used as floors, driveways, pathways, patio areas, garage pads, and structural foundations. Slabs range from thin 75 mm decorative paths to 300 mm thick structural floor slabs in multi-storey buildings. Calculating the correct volume before ordering concrete is essential to avoid costly waste or disruptive shortages during the pour.
Concrete is sold by volume — either in cubic metres (m³) from a ready-mix truck, or as premix bags sold by weight (kg) from hardware stores. Knowing your required volume in m³ allows you to place an accurate order with a concrete supplier, while knowing the bag count lets you plan a DIY pour using bagged premix. For land area calculations related to your construction project, see also acres to square metres converter.
Volume = Length × Width × Thickness — All three dimensions must be in the same unit before multiplying. Always add a 10% waste allowance to your calculated volume when ordering concrete to account for spillage, uneven subgrade, and variations in formwork. Never order exactly the calculated minimum.
The volume of a rectangular concrete slab is calculated by multiplying its three dimensions together. The key requirement is that all dimensions must be in the same unit before multiplying. For metric calculations, convert thickness from millimetres to metres by dividing by 1,000 before applying the formula.
Example: Slab 6 m × 4 m × 100 mm thick
Thickness = 100 ÷ 1000 = 0.1 m
Net volume = 6 × 4 × 0.1 = 2.4 m³
With 10% waste = 2.4 × 1.10 = 2.64 m³ to order
Box heights represent slab thickness proportionally — wider boxes indicate larger pour area
Use this quick-reference table to estimate concrete volumes for common slab sizes at standard thicknesses. All volumes include a 10% waste allowance. For custom dimensions, use the calculator above.
| Slab Size | Thickness | Net Volume (m³) | +10% Waste (m³) | 25 kg Bags |
|---|---|---|---|---|
| 2 m × 2 m | 100 mm | 0.40 m³ | 0.44 m³ | ~53 bags |
| 3 m × 3 m | 100 mm | 0.90 m³ | 0.99 m³ | ~119 bags |
| 4 m × 4 m | 100 mm | 1.60 m³ | 1.76 m³ | ~211 bags |
| 6 m × 4 m | 100 mm | 2.40 m³ | 2.64 m³ | ~317 bags |
| 6 m × 6 m | 100 mm | 3.60 m³ | 3.96 m³ | ~475 bags |
| 10 m × 6 m | 100 mm | 6.00 m³ | 6.60 m³ | ~792 bags |
| 3 m × 3 m | 150 mm | 1.35 m³ | 1.49 m³ | ~179 bags |
| 6 m × 4 m | 150 mm | 3.60 m³ | 3.96 m³ | ~475 bags |
| 6 m × 6 m | 150 mm | 5.40 m³ | 5.94 m³ | ~713 bags |
| 10 m × 6 m | 150 mm | 9.00 m³ | 9.90 m³ | ~1,188 bags |
| 6 m × 4 m | 200 mm | 4.80 m³ | 5.28 m³ | ~634 bags |
| 10 m × 6 m | 200 mm | 12.00 m³ | 13.20 m³ | ~1,584 bags |
Understanding concrete volumes becomes much easier when you relate them to common construction projects. The following examples show typical slab sizes, thicknesses, and concrete requirements for projects commonly undertaken by homeowners, builders, and contractors in 2026.
A standard single car garage slab is approximately 6 m × 3.5 m × 100 mm thick, requiring a net volume of 2.1 m³. With 10% waste allowance, you would order 2.31 m³ from a ready-mix supplier. At 25 kg bags, this equates to roughly 277 bags — making a ready-mix truck delivery far more practical and cost-effective for this size project.
A typical small home slab of 12 m × 10 m × 100 mm has a net volume of 12 m³. With 10% waste this becomes 13.2 m³ — well above the 1 m³ minimum truck delivery threshold. House slabs are always poured by ready-mix truck, often with multiple truck loads. A 200 m² home on a 100 mm slab needs approximately 20–22 m³ of concrete.
A typical residential driveway measuring 10 m × 3 m × 100 mm requires a net volume of 3 m³, or 3.3 m³ with 10% waste. Driveways subject to vehicle loads often use 125–150 mm thickness, which would increase this to 3.75–4.5 m³ net. This volume is generally at the minimum threshold for a ready-mix order — smaller volumes may be more economical with bagged premix.
A garden path measuring 10 m × 1 m × 75 mm thick requires only 0.75 m³ net volume, or 0.825 m³ with 10% waste. At this small volume, bagged premix is the practical choice — approximately 99 bags of 25 kg premix would be needed. A 75 mm path thickness is adequate for foot traffic but should be increased to 100 mm for wheelbarrow or light vehicle access.
A single cylindrical post footing 300 mm diameter × 600 mm deep has a volume of approximately 0.042 m³ (π × 0.15² × 0.6). For a deck with 10 footings, the total volume is about 0.42 m³ — requiring roughly 50 bags of 25 kg premix. Post footings are almost always poured using bagged concrete mixed on-site due to their small individual volumes.
A commercial warehouse floor of 50 m × 30 m × 150 mm requires a net volume of 225 m³. With 10% waste this is 247.5 m³ — requiring many ready-mix truck deliveries of approximately 8 m³ each, totalling around 31 truck loads. Large commercial pours require careful scheduling with the concrete supplier to ensure continuous placement before the concrete begins to set.
Choosing the correct slab thickness is as important as calculating the volume accurately. Using too thin a slab risks cracking and structural failure, while an unnecessarily thick slab wastes concrete and increases cost. The following guidelines reflect standard Australian and international construction practice for 2026.
Our concrete slab volume calculator is designed for quick, accurate results on any device. Follow these steps to calculate your concrete requirements in under a minute.
The Concrete Institute provides technical guidance on mix design, slab thickness, reinforcement, and curing — the authoritative reference for concrete construction standards used in this calculator.
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