Procedure to calculate materials required for concrete 1 2 4 ratio and a online calculator

Calculation of materials required is to be done by a site engineer in order to purchase the materials like cement, sand, course aggregates well before work starts.   This is one of the basic question asked by interviewers .

Consider 1 m3 volume of concrete

Ratio of concrete = 1:2:4

Add 30% for allowance for shrinkage after adding water and voids in concrete

Total volume = 1+(1*30/100) =1.3 m3

Cement = 1.3/(1+2+4) = 0.186 m3 = ( cement = 1440 kg/m3) so 267 kg = 5.35 no of 50 kg bags

Sand =0 .186 * 2 =0.371 m3

Course aggregates = 0.186 * 4 =0.743 m3

cement sand course aggregates required for concrete 1 2 4 ratio

Ratio of concrete
volume of concrete		m3
Add allowance for shrinkage		%
Total volume		m3
Materials	m3	kg	*Bags
Cement
Sand
Course aggregates