Choosing the right concrete grade is the most critical decision in any construction project. Whether you are pouring a simple patio or building a multi-story column, using the wrong mix can lead to structural failure or unnecessary costs.
In this guide, we will break down what “M20” or “M25” actually means, the standard mix ratios, and where to use each grade.
What Does “M” Stand For?
When you see a grade like M20, it consists of two parts:
M: Stands for Mix. It represents the specific ratio of Cement, Sand, and Aggregates.
20: Stands for the Characteristic Compressive Strength of the concrete cube in MPa (N/mm²) after curing for 28 days. (Simply put: M20 concrete can withstand a pressure of 20 Newtons per square millimeter).
Common Concrete Grades & Mix Ratios
1. Ordinary Concrete (M10, M15, M20)
These grades are typically used for general construction and non-structural works.
M10 (Ratio 1:3:6)
Uses: Levelling course, bedding for footings, P.C.C. (Plain Cement Concrete). It is used just to provide a smooth surface, not to carry heavy loads.
M15 (Ratio 1:2:4)
Uses: P.C.C. for floors, simple pavements, and residential blind concrete.
M20 (Ratio 1:1.5:3)
Uses: This is the most popular grade for residential R.C.C. (Reinforced Cement Concrete) work. Used for slabs, beams, columns, and footings in small to medium-sized buildings.
2. Standard Concrete (M25, M30, M35…)
These are high-strength mixes used for heavier loads and critical structures.
M25 (Ratio 1:1:2)
Uses: Heavy-load R.C.C. work, industrial floors, and foundations requiring extra strength.
M30 & Above (Design Mix)
Uses: Commercial high-rises, bridges, and severe weather exposure. These usually don’t have a fixed ratio (Nominal Mix) but are designed specifically in labs (Design Mix).
Quick Mix Ratio Table (Cement : Sand : Aggregate)
| Grade | Ratio | Application |
| M10 | 1 : 3 : 6 | P.C.C., Bedding |
| M15 | 1 : 2 : 4 | Flooring, Small Foundations |
| M20 | 1 : 1.5 : 3 | Slabs, Beams, Columns (Standard) |
| M25 | 1 : 1 : 2 | Heavy R.C.C. Structures |
How Much Material Do You Need?
Knowing the grade is step one. But calculating the exact volume of concrete and the number of cement bags is where site engineers struggle.
Instead of manual calculation errors, use our free tool to get instant results:
Conclusion
For most residential construction (like your house slab or pillars), M20 is the safe and standard choice. For non-structural flooring, M15 is sufficient. Always ensure you cure the concrete properly for 28 days to achieve the full strength promised by the “M” number.
Have more questions about site engineering? Check out our Tools section for more smart calculators.