Enter your concrete volume and mix ratio to get the exact number of cement bags, tonnes of sharp sand, and tonnes of granite you need — with current Nigerian material costs.
General Purpose (20 N/mm²) — the most common mix in Nigerian residential construction. Suitable for ground slabs, lintels, and general structural work.
1 m³ = approx. one column bay or 6 m² of 150mm slab
Enugu market rates. Lagos & Abuja may differ by 10–20%.
Mix 1:2:4 · 1 m³ concrete
₦109,322
₦109,322 per m³
Dry volume
1.54 m³
incl. shrinkage factor 1.54
7
bags of 50 kg
≈ 350 kg total
₦84,000
at ₦12,000/bag
0.74
tonnes
≈ 0.46 m³ loose
₦5,174
at ₦7,000/tonne
1.39
tonnes
≈ 0.92 m³ loose
₦24,948
at ₦18,000/tonne
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A concrete mix ratio describes the proportions of cement, sharp sand (fine aggregate), and granite (coarse aggregate) by volume. Written as cement : sand : granite, the ratio tells you how many parts of each material you need for every part of cement. A 1:2:4 mix, for example, means one part cement, two parts sand, and four parts granite — the most common specification for residential buildings across Nigeria.
The ratio directly controls concrete strength. Higher cement content (a "rich" mix like 1:1.5:3) produces denser, stronger concrete capable of bearing greater structural loads, while a "lean" mix (1:4:8) uses far less cement and is only suitable for non-structural filling. Nigerian structural engineers specify the mix ratio in drawings as part of the concrete grade — Grade C25 corresponds roughly to a 1:1.5:3 nominal mix, while Grade C20 is achieved with 1:2:4.
One of the most important concepts in this calculation is the dry volume factor of 1.54. When cement, sand, and granite are mixed, the fine particles fill the voids between the coarser ones, and water fills additional micro-voids — the fresh concrete occupies significantly less volume than the dry ingredients did separately. To produce 1 m³ of compacted concrete, you must start with approximately 1.54 m³ of dry materials. Every accurate concrete quantity calculation must account for this shrinkage.
Common mistakes in Nigerian construction include using a weaker mix to save on cement cost (particularly substituting 1:3:6 where 1:2:4 is required for structural elements), measuring by headpan or bucket without calibrating the volumes, and adding excess water to make the mix easier to place. Excess water dramatically weakens concrete — a water-cement ratio above 0.6 can reduce 28-day strength by 30% or more. Always use the minimum water needed for workability, and add plasticisers rather than water if the mix is stiff.
When choosing a mix ratio for your project, follow the structural engineer's specification on the approved drawing. If you do not have drawings, the rule of thumb widely used on Nigerian sites is: 1:2:4 for all reinforced elements, 1:3:6 for blinding and mass concrete. Never use a lean mix for columns, beams, or suspended slabs regardless of cost pressure.
The table below shows the quantities of each material per 1 m³ of finished concrete for each standard mix ratio (no waste factor included):
| Mix Ratio | Use Case | Cement Bags/m³ | Sand (m³) | Granite (m³) |
|---|---|---|---|---|
| 1:1.5:3 | Structural (columns, beams, slabs) | ~10.5 | 0.475 | 0.95 |
| 1:2:4 | General purpose structural work | ~8.0 | 0.51 | 1.03 |
| 1:3:6 | Blinding / mass concrete | ~5.5 | 0.52 | 1.04 |
| 1:4:8 | Lean mix / hardcore blinding | ~4.4 | 0.56 | 1.12 |
Figures based on dry volume factor of 1.54 and 50kg cement bags (volume ≈ 0.035 m³ per bag). Actual site yields vary with aggregate grading and workmanship.
The water-cement (w/c) ratio is the single most important factor controlling concrete strength and durability. It is the mass of water added to a mix divided by the mass of cement. A ratio of 0.5 means 25 litres of water per 50 kg bag of cement — this is the standard design value for most Nigerian construction.
The relationship between w/c ratio and strength is inverse: as you increase the water content, strength drops. This is because excess water creates additional capillary pores in the hardened cement paste, reducing the density and load-carrying capacity of the matrix. A mix designed at w/c = 0.5 achieving 25 N/mm² may fall to 15–18 N/mm² if water is freely added to improve workability, putting structural elements at serious risk.
On Nigerian construction sites, the most common defect is workers adding water to stiffen mixes that have partially set or become unworkable in the heat. This "re-tempering" must never be done — discard any concrete that has stiffened past the point of easy placement. In the Nigerian climate, concrete should generally be mixed and placed within 30–45 minutes of water being added.
Recommended w/c ratios for Nigerian conditions: 0.45–0.50 for exposed structural elements (foundation columns, external slabs), 0.50–0.55 for protected interior elements, and never above 0.60 for any reinforced concrete. When the mix is too stiff at w/c = 0.5, use a plasticiser admixture rather than extra water to restore workability.
Proper curing is equally critical — uncured concrete loses moisture to evaporation in Nigeria's dry seasons, stunting the hydration process that builds strength. Cover all freshly placed concrete with wet hessian or polythene sheeting and keep it wet for at least 7 days, ideally 14–28 days for structural elements. Concrete gains approximately 70% of its 28-day strength in the first 7 days, but curing must continue beyond this period to minimise cracking from thermal and drying shrinkage.