Which RMC grade should you choose?
Published 6 August 2026 · Mathrani Mining & Infrastructure
Every RMC order form asks the same question first: which grade. The number after the M is the 28-day characteristic compressive strength in N per square millimetre, tested on a standard cube to IS 456. Beyond that, most of the confusion on site comes from picking a grade by habit rather than by what the member actually has to carry.
Start from the member, not the budget
A higher grade costs more per cubic metre, so there is a temptation to specify low across the board and save money, or to specify high everywhere out of caution. Both waste money in different directions. The grade should follow the structural design for that member, and the structural design should already state it. If it does not, this is the working guide we use with clients who are building without a structural drawing in hand.
| Grade | 28-day strength | Typical use |
|---|---|---|
| M10 | 10 N/mm² | Levelling course, blinding below footings |
| M15 | 15 N/mm² | Plain flooring, kerbs, pathways |
| M20 | 20 N/mm² | Residential slabs, columns and beams |
| M25 | 25 N/mm² | Standard RCC frames, footings, retaining walls |
| M30 | 30 N/mm² | Multi-storey frames, water tanks |
| M35 – M40 | 35 – 40 N/mm² | High-rise columns, rafts, bridge decks |
| M45 – M50 | 45 – 50 N/mm² | Piers, prestressed girders, heavy infrastructure |
Three questions that settle it
If you take nothing else from this guide, take these three questions to your structural engineer or, if there is none, use them as a sanity check before you place the order.
- What is directly above or on this member? A footing under a two-storey house and a footing under a water tank are not the same footing, even if they look the same size.
- Is it exposed to weather or water? Exposure pushes the minimum grade up regardless of load, because durability and strength are governed together in IS 456.
- Does it need to be pumped or does it sit in congested steel? This affects workability and mix design more than grade, but it is worth raising with us at the same time so the mix is right on the first load.
Where people over-order
The commonest over-order we see is M25 used for plain footpaths and boundary plinths that would perform perfectly well at M15 or M20. It is not a large saving on one slab, but it adds up across a whole compound wall or a housing layout, and the cement content in the higher grade is doing nothing for a slab that will never be loaded that way.
Where people under-order
The commonest under-order is on water-retaining and below-grade structures, where M20 gets specified because it matches the columns above, without accounting for the durability requirement of permanent water contact. This is the one place we always ask what the member actually touches before we confirm the grade.
Getting the mix right, not just the number
Grade sets the strength target. Slump, admixture dosage and aggregate size still have to be set for how the concrete will actually be placed on your day, your haul distance and your weather. That is the conversation worth having with your supplier before the pour, not after the first load arrives too stiff or too wet.
Send us the member, the load and the exposure and we will confirm the grade before you order. Full grade table and special mixes on the ready-mix concrete page.
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