M20, one cubic metre: the familiar 8.06 bags
- Wet concrete volume (m³)
- 1
- Mix grade
- M20 (1 : 1.5 : 3)
- Dry volume factor
- 1.54
- Cement bag size (kg)
- 50
Cement bags8.06
DRV-017 verified table
Open this exampleConstruction & HomematerialsIndia only
Concrete Mix Ratio Calculator
Cement, sand and aggregate for a concrete pour, with the 1.54 dry-volume factor exposed as an input rather than buried as a constant. M20 works out at 8.06 bags per cubic metre.
Also called: cement sand aggregate ratio, m20 concrete mix.
Cement bags
8.06
8.06 bags of cement, 0.42 m³ of sand and 0.84 m³ of aggregate for 1 m³ of M20 concrete. The dry volume is 1.54 m³. More than the wet volume, because water fills the voids between particles.
Cement (kg)
403.2
Cement (m³)
0.28
Sand (m³)
0.42
Aggregate (m³)
0.84
Dry volume (m³)
1.54
Method and background
How this is calculated
Dry ingredients occupy more volume than the wet concrete they produce, because water fills the voids between particles. The 1.54 factor combines sand bulking of about 20% with aggregate voids of about 34%; field values range from 1.52 to 1.57, which is why it is an input here. Cement density is taken as 1440 kg/m³, and the familiar "about eight bags per cubic metre for M20" falls straight out of that.
dry = wet * 1.54; cement_kg = dry * (a/sum) * 1440; bags = cement_kg / 50- a : b : c
- The mix ratio
- sum
- Sum of the ratio parts
Full derivation: Concrete quantities, and where the 1.54 comes from
Worked examples
Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.
M15 uses less cement
- Wet concrete volume (m³)
- 1
- Mix grade
- M15 (1 : 2 : 4)
- Dry volume factor
- 1.54
- Cement bag size (kg)
- 50
Cement bags6.34
1.54 x 1/7, independently computed
Open this examplezero volume needs nothing
- Wet concrete volume (m³)
- 0.01
- Mix grade
- M20 (1 : 1.5 : 3)
- Dry volume factor
- 1.54
- Cement bag size (kg)
- 50
Cement bags0.08
degenerate case: scales linearly
Open this exampleMethod and limits
What it assumes
- Cement density 1440 kg/m³.
- The dry-volume factor accounts for sand bulking and aggregate voids; 1.54 is the standard convention.
What it deliberately does not model
- Nominal mix proportions only. A design mix for a specific strength and workability is a laboratory exercise, not a ratio.
- No allowance for wastage, add 3–5% on site.
Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator