Concrete Mix Ratio & Slump Reference
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Pick a grade to see its mix proportion, typical cement content and water-cement ratio — and use the slump table to match workability to the job. Nominal mixes up to M20 are IS 456 Table 9; M25 and above are design mixes (IS 10262).
Concrete Mix & Slump Reference (IS 456)
Grade → proportion, cement content and w/c · plus slump & workability
Slump test
Workability by the fall of the cone
Grade
M20
Proportion
1:1.5:3
Cement content
~300 kg/m³
Water–cement
0.50–0.55
Typical use
House RCC — the default
M20 concrete
1:1.5:3
Nominal mix (IS 456 Table 9) · cement ~300 kg/m³ · w/c 0.50–0.55
Nominal mixes & typical design content
M10
1:3:6
~220 kg/m³
M15
1:2:4
~250 kg/m³
M20
1:1.5:3
~300 kg/m³
M25
Design mix
~330 kg/m³
M30
Design mix
~360 kg/m³
M35
Design mix
~400 kg/m³
M40
Design mix
~430 kg/m³
Slump & workability (IS 456)
| Placement | Slump | Workability |
|---|---|---|
| Mass concrete, pavements | 25–50 mm | Very low – low |
| RCC beams, slabs, columns | 50–100 mm | Medium |
| Heavily reinforced sections | 75–125 mm | Medium – high |
| Pumped concrete | 100–150 mm | High |
| Tremie / underwater | 150–200 mm | Very high |
Nominal mixes stop at M20 (IS 456 Table 9). The proportions for M25 and above must be a design mix (IS 10262), proportioned from your actual materials and confirmed on trial batches — the cement content and w/c above are typical values to expect, not a recipe. Turn a grade into bags on the concrete calculator.
Nominal mix ratios (IS 456 Table 9)
| Grade | Ratio (cement:sand:aggregate) | Typical cement | w/c |
|---|---|---|---|
| M10 | 1:3:6 | ~220 kg/m³ | 0.55–0.60 |
| M15 | 1:2:4 | ~250 kg/m³ | 0.50–0.55 |
| M20 | 1:1.5:3 | ~300 kg/m³ | 0.50–0.55 |
| M25+ | Design mix (IS 10262) | 330 kg/m³ and up | 0.45 and below |
Nominal mixes stop at M20. From M25 the ratio must be proportioned by design from your actual materials and confirmed on trial batches — the figures above are what to expect, not a recipe.
Slump & workability (IS 456)
| Placement | Slump | Workability |
|---|---|---|
| Mass concrete, pavements | 25–50 mm | Very low – low |
| RCC beams, slabs, columns | 50–100 mm | Medium |
| Heavily reinforced sections | 75–125 mm | Medium – high |
| Pumped concrete | 100–150 mm | High |
| Tremie / underwater | 150–200 mm | Very high |
Frequently asked questions
What is the mix ratio for M20 concrete? 1:1.5:3 (cement : sand : aggregate) as a nominal mix — the default for house RCC. From M25 upward the ratio is set by a design mix, not a fixed proportion.
What is a good slump for RCC? 50–100 mm for ordinary beams, slabs and columns. Higher slump is easier to place but, if achieved by adding water instead of admixture, weakens the concrete.
Why can't I use a nominal mix above M20? IS 456 only tabulates nominal mixes to M20. Higher grades need the cement, water and aggregate proportioned to the target strength and tested — a nominal ratio can't guarantee M25+.
Does more slump mean weaker concrete? Only if the extra flow comes from water. Adding water raises the water-cement ratio and cuts strength; a plasticiser raises slump without adding water.
Related
CivilSite Editorial Team✓ Engineer reviewed
Written and reviewed by practising civil engineers with 10+ years of Indian residential construction experience.