To make one cubic yard of concrete, you typically need about 7 x 94lb bags of Portland cement, 14 cubic feet of sand, 21 cubic feet of gravel (crushed stone) and approximately 32 gallons of clean water depending on the desired strength and consistency of the concrete mix.
The typical mix ratio for concrete is 1 part cement, 2 parts sand, and 3 parts gravel or crushed stone, by volume. A cubic yard of concrete is equal to 3 feet in length by 3 feet in width by 3 feet in thickness which is equal to 27 cubic feet.
A bag of Portland cement weighs about 94 pounds, which is approximately equivalent to 1 cubic foot. To make one cubic yard (27 cubic feet) of solid slab of concrete, you typically need about 27 x 1.54 = approx. 41.58 cubic feet of dry ingradients (mixture of cement, sand and gravel) of concrete due to shrinkage properties.
The amount of water needed per bag of cement depends on how dry or wet the sand is. If it’s already moist, you’ll need about 4-1/2 gallons of clean water per bag of cement and if it is dry, you’ll need about 6 gallons of water per 94 lb bag of Portland cement.
How much concrete will a 94 lb bag of Portland cement make? A 94-pound bag of Portland cement makes about 4.5 cubic feet of concrete. An ideal concrete mix ratio is 1 cubic foot (94 lb) of cement mix with 2 cubic feet of sand and 3 cubic feet of gravel for a total of 6 cubic feet of dry ingredients; after adding water its only yields about 4.5 cubic feet volume of concrete.
To make an ideal concrete mix at 3500 PSI, you need to mix 1 part Portland cement (94 lbs) with 2 parts sand (160 to 180 lbs) and 3 parts gravel or crushed stone (240 to 300 lbs) and 6 gallons of clean water with some additives.
Here’s is general calculation steps for how many bags of Portland cement to make a yard of concrete:-
- Estimate dry volume of concrete: To calculate dry volume of concrete, you need to multiply 1.54 numerical figure to wet volume of concrete, so formula for dry volume = wet volume x 1.54, means to make one cubic yard of concrete, you typically need about 1.54 cubic yards of dry ingradients of concrete.
- Estimate proportion of dry ingradients of concrete: Total proportion of an ideal mix is 1+2+3 = 6, so parts of cement = 1/6, parts of sand = 2/6, and parts of gravel = 3/6.
- Estimate quantity of cement: Cement quantity in cubic yards = 1.54/6 = 0.257 cubic yards, or cement quantity in cubic feet = 0.257 x 27 = 6.93 or nearly 7 cubic feet, or which is equal to 7 bags of 94 lb (1 cubic foot) of Portland cement.
- Estimate quantity of sand: Sand quantity in cubic yards = (2/6) x 1.54 = 0.513 cubic yards, or sand quantity in cubic feet = 0.513 x 27 = 13.86 or nearly 14 cubic feet.
- Estimate quantity of gravel: Stone quantity in cubic yards = (3/6) x 1.54 = 0.77 cubic yards, or gravel quantity in cubic feet = 0.77 x 27 = 20.79 or nearly 21 cubic feet.
- Estimate quantity of water: The general water cement ratio is 0.5 to 0.6, so required volume of water = 7 x 0.5 x 7.4805 = 26 gallons, or 7 x 0.6 x 7.4805 = 32 gallons.
Conclusions:
To make 1 cubic yard of concrete paste, you’d need to mix 7 x 94-pound bags of cement, about 1/2 cubic yard (14 cubic feet) of sand and just over 3/4 cubic yard (21 cubic feet) of gravel and 32 gallons of clean water.