How many cement bags are needed per m³ of concrete?

For standard concrete (250 kg/m³ mix), you need 5 bags of 50 kg per m³. For structural concrete (300 kg/m³), use 6 bags. This calculator uses the typical dosage for each element type.

Why should I add a wastage percentage?

On-site losses from spillage, unusable mixes and level corrections always occur. Adding 5–10 % to your final order ensures you don't run short of material.

What is the difference between mass concrete and reinforced concrete?

Mass concrete has no steel reinforcement and is used for low-load foundations. Reinforced concrete includes steel bars that provide tensile strength, making it suitable for slabs, columns and beams.

Reinforced Concrete Calculator

Last updated: 2026-05-09

Use the Reinforced Concrete Calculator to get instant, accurate results. Enter your values below.

Inputs

Dimensions

Length (m) (m)

Width (m) (m)

Thickness (m) (m)

Material / Product

Steel ratio (kg/m³) (kg/m³)

Wastage Allowance (%)

Result

Enter values and press Calculate

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Common Sizes — Click to Fill

Length (m) (m)	Width (m) (m)	Thickness (m) (m)	Steel ratio (kg/m³) (kg/m³)
3 m	3 m	0.15 m	80 kg/m³
4 m	4 m	0.15 m	100 kg/m³
5 m	5 m	0.2 m	120 kg/m³
6 m	4 m	0.2 m	120 kg/m³
10 m	5 m	0.2 m	100 kg/m³

Popular combinations

Reinforced Concrete 3×2m Slab 0.15m Thick Reinforced Concrete 3×3m Slab 0.25m Thick Reinforced Concrete 5×2m Slab 0.15m Thick Reinforced Concrete 8×2m Slab 0.15m Thick Reinforced Concrete 8×3m Slab 0.25m Thick Reinforced Concrete 10×2m Slab 0.15m Thick Reinforced Concrete 10×3m Slab 0.2m Thick Reinforced Concrete 10×5m Slab 0.3m Thick

What is Reinforced Concrete?

Reinforced concrete combines concrete's compressive strength with steel's tensile strength. It's used for beams, columns, slabs, and foundations where both compression and tension forces are present. The steel reinforcement carries tensile loads while the concrete handles compression.

Volume and Steel Calculation

Volume (m³) = Length (m) × Width (m) × Thickness (m)

Steel (kg) = Volume (m³) × Steel density (kg/m³)

Typical steel densities: beams 100-150 kg/m³, slabs 80-120 kg/m³, columns 120-200 kg/m³, foundations 60-100 kg/m³.

Worked Example

A structural slab 6m × 4m × 0.25m with 120 kg/m³ steel:

Volume = 6 × 4 × 0.25 = 6 m³
Cement = 6 × 7 = 42 bags
Steel = 6 × 120 = 720 kg
Sand = 6 × 0.55 = 3.30 m³
Gravel = 6 × 0.80 = 4.80 m³

Common Mistakes

Underestimating steel density for critical structural elements
Insufficient concrete cover (minimum 3cm for interior, 4cm for exterior)
Poor vibration leading to honeycombing and weak spots
Wrong rebar placement — tension steel must be in the tension zone

Standards

Calculated per EN 1992-1-1 (Eurocode 2) / ACI 318.

Written and reviewed by the CalcToWork editorial team. Last updated: 2026-05-09.