It depends on the Grade of Concrete.
general grades are M15, M20, M25 etc.
here are the nos. of bag required
-------------------Bag for 1 cum---------------Bag for 5 cum
M15------------------- 6.4----------------------------32
M20-------------------- 8-----------------------------40
M25--------------------12----------------------------60
30
36
To calculate the amount of cement needed, first convert the dimensions of the sidewalk into cubic yards. The sidewalk's volume is ( \frac{4}{12} ) feet thick × 3 feet wide × 40 feet long = 40 cubic feet. Since there are 27 cubic feet in a cubic yard, the volume in cubic yards is ( \frac{40}{27} \approx 1.48 ) cubic yards. At $76 per cubic yard, the total cost would be approximately ( 1.48 \times 76 \approx 112.48 ).
Cement content varies on concrete type, but is typically 400kg per cubic metre. According to the manufacturer, Portland Cement (which is what 99.9% of all cement actually is) has a density of 1505kg/cubic meter.
7 cement bags per 1 cubic meter of concrete......
30
Forty five 80 pound bags of cement are needed to make one cubic yard of concrete.
20' by 26' by 5" requires at least 10 cubic yards of cement.
4 bags of 50 kg each= 200 kg of cement.
You will need 27.6 cubic yards of cement.
You will need at least 9.68 cubic yards of cement.
M20 - 6.20bags
A minimum of 5.93 cubic yards is needed.
14.81 cubic yards.
0.86 cubic yards is needed.
3.95 cubic yards of cement are needed for a slab that size.
A total of 3,250,000 cubic yards.