How do I calculate how much concrete I need in South Africa?

Concrete volume is calculated as Length × Width × Depth in metres, giving a result in cubic metres (m³). For a driveway slab of 6m × 3m × 0.1m (100mm thick), you need 1.8m³ of concrete. Always add 10% for wastage and spillage. Ready-mix concrete is ordered in m³ — most suppliers have a minimum order of 0.5–1m³.

How many bags of cement do I need per cubic metre of concrete?

For a 1:2:3 mix, approximately 6–7 bags of 50kg cement are needed per m³ of concrete. For a weaker 1:3:6 mix, approximately 3–4 bags per m³ are needed. These figures account for the fact that aggregate fills some of the void, so you need less cement volume than the dry mix suggests. Ready-mix suppliers calibrate this precisely.

How thick should a concrete driveway slab be in South Africa?

For a residential driveway carrying standard passenger vehicles, a minimum slab thickness of 100mm (10cm) is recommended in South Africa. For heavier vehicles such as bakkies, trucks or heavy SUVs, increase to 150mm. Slabs should be reinforced with BRC mesh (193 or 283 grade) and have a compacted sub-base of at least 100mm of G5 or crusher run material.

Should I mix my own concrete or use ready-mix in South Africa?

For volumes under approximately 1m³, mixing on-site with a mixer is cost-effective. For volumes above 1–2m³, ready-mix concrete from a batching plant is almost always more economical and produces a more consistent, quality-controlled product. Ready-mix costs approximately R1,800–R2,400 per m³ (2026) depending on province and strength grade. The labour saving alone often justifies ready-mix for larger pours.

What is the concrete volume for a standard house foundation in South Africa?

A typical strip foundation for a 3-bedroom house is approximately 400mm wide × 200mm deep (or deeper depending on soil conditions). For a house with a 50m perimeter, this gives roughly 50m × 0.4m × 0.2m = 4m³ of concrete just for the strip. A structural engineer should specify foundation depth and width based on actual soil bearing capacity.

Concrete Volume Calculator South Africa — Slabs, Foundations & Driveways

🏗️ Last Updated: May 2026 · SA Mix Ratios & Ready-Mix Pricing

🏗️Concrete Calculator — Enter Element Details

Element Type

Length (metres)Longest dimension

Width (metres)Shortest dimension

Thickness / Depth (mm)100mm = standard residential slab

Quantity (number of elements)For multiple columns or pads

Mix Type

Wastage Factor

Total Concrete Required (inc. wastage)

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Net Volume

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Cement (50kg bags)

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Sand (m³)

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Stone (m³)

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Ready-mix to Order

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Ready-mix Est. Cost

⚠️ For planning purposes only. Consult a structural engineer or contractor before pouring structural concrete.

Concrete Calculations in South Africa — Complete Guide

Concrete is the most fundamental building material in South African construction, used for foundations, slabs, driveways, columns, paths, and pools. Getting the volume calculation right before you order is critical — too little concrete means a cold joint (a structural weakness) if you have to stop and wait for more, and over-ordering is expensive waste.

SA Concrete Mix Ratios Explained

Mix Ratio	Cement:Sand:Stone	Strength (approx)	Best Use
1:2:3	1 bag : 2 parts : 3 parts	~25 MPa	Foundations, columns, beams, structural slabs
1:4:4	1 bag : 4 parts : 4 parts	~20 MPa	Driveways, pathways, general floor slabs
1:3:6	1 bag : 3 parts : 6 parts	~15 MPa	Blinding layers, mass fill, non-structural
20 MPa ready-mix	Factory batched	20 MPa	Residential slabs, driveways, general use
25 MPa ready-mix	Factory batched	25 MPa	Structural elements, engineer-specified

Concrete Volume Formula

Formula

Volume (m³) = Length (m) × Width (m) × Depth (m) × Quantity Order quantity = Net volume × Wastage factor (min 1.10) Cement bags (1:2:3) = Volume × 6.5 bags per m³ Sand (m³) = Volume × 0.44 (1:2:3 mix) Stone (m³) = Volume × 0.66 (1:2:3 mix)

Slab Thickness Guide for SA Conditions

Pathways (pedestrian only): 75–100mm minimum, no reinforcement needed for short spans
Residential driveway (passenger cars): 100mm minimum with BRC mesh reinforcement
Driveway (bakkies/heavy vehicles): 150mm with BRC mesh and compacted sub-base
House floor slab: 100–125mm with BRC mesh on compacted fill
Strip foundation: 200mm deep minimum — engineer to specify based on soil
Sub-base under any slab: 100mm compacted G5 or crusher run

Ready-Mix vs Site-Mixed Concrete in South Africa

Ready-mix concrete (ordered from a batching plant and delivered by truck mixer) is the standard choice for volumes above 1–2m³ in South Africa. It is more consistent, higher quality, and often more cost-effective once you account for the labour to mix on site. Ready-mix is priced per m³ — expect to pay approximately R1,800–R2,400/m³ for 20MPa in 2026, varying by province and supplier. Most batching plants require a minimum order of 3–6m³.

For small volumes (under 1m³), mixing on-site with a drum mixer is practical. Use a consistent scoop measure for cement, sand and stone — never estimate by eye, as inconsistent mixes produce weak concrete.

Frequently Asked Questions

How do I calculate how much concrete I need?

Concrete volume = Length × Width × Depth in metres, giving m³. For a 6m × 3m slab at 100mm thick: 6 × 3 × 0.1 = 1.8m³. Always add 10% wastage, so order 2.0m³. Use this calculator to handle multiple elements and get cement, sand and stone quantities automatically.

What is the standard concrete mix ratio in South Africa?

The most common SA mix ratios are: 1:2:3 (structural — foundations, columns, beams); 1:4:4 (general slabs and driveways); 1:3:6 (blinding and non-structural fill). Ready-mix is specified in MPa — 20MPa is standard for residential work, 25MPa for structural elements.

How many bags of cement per cubic metre of concrete?

For a 1:2:3 mix approximately 6–7 bags of 50kg cement per m³. For a 1:4:4 mix approximately 4–5 bags per m³. For a weak 1:3:6 blinding mix approximately 3–4 bags per m³.

How thick should a concrete driveway be in South Africa?

For standard passenger vehicles: minimum 100mm (10cm) with BRC mesh reinforcement on a 100mm compacted sub-base. For bakkies and heavier vehicles: increase to 150mm. Always compact the sub-base thoroughly before pouring — concrete on soft ground will crack regardless of thickness.

Should I use ready-mix or mix my own concrete?

For volumes over 1–2m³, ready-mix is almost always more economical when labour is included. It costs approximately R1,800–R2,400/m³ (2026) and produces consistent, quality-controlled concrete. For small jobs under 1m³, site-mixing is practical. Most batching plants have a minimum order of 3–6m³.

Do I need reinforcement in my concrete slab?

Yes — all driveways and floor slabs in South Africa should include BRC mesh reinforcement (typically 193 or 283 grade) to control cracking. The mesh is placed at mid-slab depth on bar chairs. Structural slabs carrying loads (suspended slabs, garage slabs, pool surrounds) should be designed by a structural engineer.

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Concrete Volume Calculator — South Africa