Concrete Grades Explained: M10 to M40 and Where to Use Them
Concrete grade is one of those terms clients and juniors often get wrong. Here's the simple version, with where each grade belongs.
What the grade means
M = mix, and the number = characteristic compressive strength in MPa (N/mm²) at 28 days. So M20 = 20 MPa.
Grades and nominal mixes
| Grade | Ratio | Common use |
|---|---|---|
| M10 | 1:3:6 | Levelling, PCC |
| M15 | 1:2:4 | PCC, non-structural |
| M20 | 1:1.5:3 | Residential RCC slab |
| M25 | Design mix | RCC columns, beams |
| M30–M40 | Design mix | High-load, commercial |
Nominal vs design mix
Up to M20, nominal mixes (fixed ratios) are common. M25 and above are usually design mixes proportioned by a lab for the required strength.
Don't over- or under-specify
Using M25 where M20 is enough wastes cement; under-specifying risks the structure. Follow the structural engineer's grade.
Get quantities right per grade
Each grade needs different cement, sand and aggregate. Vystra's concrete calculator gives per-grade quantities, and material tracking records what you actually used — so the mix on site matches the mix you priced.
Frequently asked questions
What does M20 concrete mean?
M20 means a concrete mix with a characteristic compressive strength of 20 MPa at 28 days. The 'M' stands for mix and the number is the strength in N/mm².
Which concrete grade is used for slab?
M20 is commonly used for residential slabs. M25 and above are used where the structural design specifies higher strength.
What is the mix ratio for M20?
The nominal mix ratio for M20 is 1:1.5:3 (cement : sand : aggregate). Higher grades like M25+ are usually design mixes.
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