Concrete & Mulch Volume Calculator
Calculate how many cubic metres of concrete, mulch, soil, or gravel you need for any project.
For circles, enter diameter
e.g. 0.1 = 100mm slab, 0.075 = 75mm mulch
Add 10% for concrete, 15–20% for mulch/soil
How to Use
1. Select the material you're ordering 2. Select your area shape 3. Enter dimensions in metres 4. Enter depth/thickness in metres (e.g. 100mm = 0.1m) 5. Add a wastage factor — 10% for concrete, 15–20% for loose materialsCommon depths:
Formula
Volume (m³) = Length × Width × Depth | Circle: π × r² × Depth | Triangle: ½ × Base × Width × DepthFrequently Asked Questions
How many 20kg bags of concrete do I need?
One 20kg premix bag makes approximately 0.0098 m³ of concrete. This calculator works it out automatically based on your volume.
How deep should mulch be?
For garden beds: 75–100mm (0.075–0.1m) suppresses weeds well. Avoid piling mulch against plant stems. Refresh annually as it breaks down.
Why add a wastage factor?
Concrete: always add 10% for spillage and variations in formwork. Bulk materials (mulch, soil, gravel): add 15–20% as loose materials compress once placed.
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