Nominal Mix vs Design Mix Concrete
“Nominal mix” and “design mix” describe two different ways of arriving at concrete proportions, and IS 456:2000 does not allow either one everywhere. This page explains the difference, when each applies, and the commonly used nominal mix proportions.
What a nominal mix is
A nominal (prescribed) mix uses fixed proportions given directly in the code, without any design calculation for the actual materials on site. IS 456:2000 permits nominal mixes only for concrete up to grade M20, and only for smaller or less critical works.
What a design mix is
A design mix has its proportions worked out for the actual materials being used, following the IS 10262:2019 method. IS 456:2000 requires a design mix for grade M25 and above. Because a design mix uses the real properties of your cement and aggregates rather than a generic ratio, it is usually more economical and more reliable than a nominal mix.
Commonly used nominal mix proportions
Proportions are cement : fine aggregate : coarse aggregate, by volume:
| Grade | Cement : Fine aggregate : Coarse aggregate |
|---|---|
| M5 | 1 : 5 : 10 |
| M7.5 | 1 : 4 : 8 |
| M10 | 1 : 3 : 6 |
| M15 | 1 : 2 : 4 |
| M20 | 1 : 1.5 : 3 |
These proportions are by volume and are deliberately conservative. Where materials are tested, the design-mix method is preferred.
Frequently asked questions
Can I use a nominal mix for M25?
No. IS 456 requires a design mix for grade M25 and above; a nominal mix is not permitted at that grade.
Why is a design mix more economical?
A design mix uses the actual properties of your materials, so it does not need to over-use cement just to stay safe the way a generic prescribed ratio does.