Convert thickness
Millimetres are divided by 1,000 before multiplying by length and width.
Free South African concrete calculator
Concrete calculator.
Order the right m³.
Calculate net volume, a practical waste allowance, ready-mix quantity, premix bags or indicative cement, sand and stone for simple pours.
Calculate concrete ↓m³Metric volume
01Slabs and
driveways
driveways
02Footings and
rectangular pours
rectangular pours
03Round columns
and piers
and piers
04Ready-mix or
bag estimates
bag estimates
01
Concrete volume
Measure the pour
Use metres for plan dimensions and millimetres for thickness. Split irregular pours into simple shapes and calculate them separately.
02
The method
Volume before materials
Concrete is ordered by finished volume. Bag and aggregate estimates come only after the geometry is correct.
Calculate net m³
Rectangles use length × width × depth; round columns use π × radius² × height.
Add an allowance
Excavation variation, spillage and uneven bases mean the clean volume is rarely the order volume.
Confirm supply
Ready-mix suppliers and premix manufacturers must confirm strength, yield and minimum order.
Safety boundary
Volume is not structural design.
This calculator cannot specify strength, reinforcement, foundation dimensions, joints or curing requirements.
See all calculators →Good to know
Concrete calculator FAQs
How do I calculate cubic metres of concrete?+
Convert every dimension to metres, then multiply length × width × thickness. For example, 6 m × 3 m × 0.1 m equals 1.8 m³ before waste.
How much extra concrete should I order?+
Ten percent is a common planning allowance for small pours, but excavation accuracy, formwork and supplier minimums matter. Confirm the final quantity before dispatch.
When should I use ready-mix?+
Ready-mix is normally preferable for larger or continuous pours because batching is controlled and the pour can proceed without repeated small mixes. Access, timing and minimum-load charges must be checked.
Does this calculate slab thickness or reinforcement?+
No. Thickness, concrete strength, reinforcement, joints and foundations are design decisions that require approved drawings or competent professional input.