Concrete Mix Ratio Calculator — Cement, Sand & Aggregate

🔧 Concrete Mix Calculator

Concrete Volume Required (m³)

Mix Ratio (Cement : Sand : Aggregate)

Standard Mix Ratios

M7.5	1:4:8	Very lean, non-structural
M10	1:3:6	Blinding / mass concrete
M15	1:2:4	General construction
M20	1:1.5:3	Standard structural
M25	1:1:2	High strength structural

Understanding Concrete Mix Ratios

A concrete mix ratio defines the proportion of cement, sand (fine aggregate), and coarse aggregate by volume. The ratio directly determines the concrete grade (strength class).

How the Calculation Works

Dry Volume = Wet Volume × 1.54
Then split by ratio parts: Cement = Dry Vol × C/(C+S+A)

For M20 (1:1.5:3) and 5 m³ of concrete:

Dry volume = 5 × 1.54 = 7.7 m³
Sum of parts = 1 + 1.5 + 3 = 5.5
Cement = 7.7 × (1/5.5) = 1.4 m³ = 40 bags
Sand = 7.7 × (1.5/5.5) = 2.1 m³
Aggregate = 7.7 × (3/5.5) = 4.2 m³

Which Grade Should I Use?

M10/M15 — blinding layers, non-structural fills
M20 — slabs, beams, columns in residential construction
M25+ — heavy structural work, bridges, high-rise — consult an engineer

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Frequently Asked Questions

What does M20 concrete mean?+

M20 means the concrete has a characteristic compressive strength of 20 N/mm² (20 MPa) at 28 days. The "M" stands for Mix. M20 uses a 1:1.5:3 ratio.

Why multiply by 1.54 for dry volume?+

Dry ingredients fill voids when mixed, reducing volume. To get 1 m³ of wet concrete, you need 1.54 m³ of dry materials. This 54% increase accounts for compaction.

How many bags of cement per m³ of M20?+

Approximately 8 bags of 50 kg cement per m³ of M20 (1:1.5:3) concrete.