MixDesignCalc 2026 — Important Clarification: M25 Has No Nominal Mix in IS 456. IS 456 Cl.9.1 Requires a Designed Mix. Here Is What M25 Actually Looks Like per IS 10262:2019 — with an Interactive Calculator.
IS 456:2000 Table 9 provides nominal mix proportions for only five grades — M5 through M20. The table stops at M20. M25 is not in the table. Not as 1:1:2, not as any ratio. The first grade that has no nominal mix option in IS 456 is M25.
| Grade | Total Quantity of Dry Aggregates per 50 kg Cement (max) | Proportion of FA to CA | Water per 50 kg Cement (max) |
|---|---|---|---|
| M5 | 800 kg | Generally 1:2 | 60 L |
| M7.5 | 625 kg | Generally 1:2 | 45 L |
| M10 | 480 kg (1:3:6) | 1:2 (FA:CA) | 34 L |
| M15 | 330 kg (1:2:4) | 1:2 (FA:CA) | 32 L |
| M20 | 250 kg (1:1.5:3) | 1:1.5 (FA:CA) | 30 L |
| ❌ M25 — NOT IN TABLE. No nominal mix exists. Designed mix mandatory per IS 456 Cl.9.1. | |||
| ❌ M30 and above — NOT IN TABLE. Designed mix mandatory. | |||
IS 456:2000 Cl.9.1 states: "Where design mixes are to be used, the mix shall be proportioned according to IS 10262." And more critically from IS 456 Cl.9.1 (fourth revision): "For grades M25 and above, the mix shall be designed as per IS 10262." This is a mandatory code requirement, not a guideline or recommendation. There are no exceptions for small pours, residential construction, or rural areas.
The ratio "1:1:2" is sometimes cited for M25 in informal construction practice, older textbooks (pre-2000), and some non-IS references. It is worth understanding where this comes from — not to validate it, but to understand why it persists:
Sometimes, yes — which makes it more dangerous, not less. A 1:1:2 mix batched with good quality cement and controlled water (w/c ≈ 0.50) might achieve 25–28 MPa cube strength. But:
1. w/c is uncontrolled — site water addition typically pushes w/c to 0.65–0.80, dropping strength to 18–22 MPa. The mix "looks like M25" during design but performs as M15 on site.
2. Durability is not addressed — even if strength is achieved, IS 456 Table 5 Moderate exposure requirements (max w/c 0.50, min cement 300 kg/m³) are not verified. A 1:1:2 mix with site water addition almost certainly exceeds w/c 0.50.
3. IS 456 Cl.9.1 is violated regardless of what strength is achieved. Code compliance requires the IS 10262 design procedure, not just achieving the cube strength number.
"What ratio should I use for M25?" is the wrong question.
The right question is: "What proportions of cement, water, FA and CA — using my specific materials — achieve 33.25 MPa mean strength, w/c ≤ 0.50 (Moderate), minimum 300 kg/m³ cement, with trial mix verification?" That is what IS 10262:2019 answers. The proportions will vary by MSA, FA zone, cement brand, and whether SP is used.
The proportions for IS 10262:2019 designed M25 depend on the specific materials used — this is why a nominal ratio cannot be given. The following shows a typical M25 designed mix for 20mm crushed granite, 100mm target slump, OPC 53, Moderate exposure, IS 383 Zone II M-Sand, without SP. Real project proportions will differ based on actual material specific gravities and aggregate zone.
M20 can use a nominal 1:1.5:3 mix (IS 456 Table 9) in Mild exposure. M25 cannot. The step from M20 to M25 is not just a 5 MPa strength increase — it is the crossing of the IS 456 Cl.9.1 threshold where designed mix becomes mandatory, where Moderate exposure is the minimum, where cover increases, and where w/c must be controlled to 0.50. This is why M25 is the first grade where proper mix design, weigh batching, and QC become non-negotiable.