You need to calculate how much concrete you need for a 3-bedroom self-contained home. Generally speaking, 350–400 kg of cement can be used to make 1 cubic meter of concrete. A bag of cement is usually 50 kg. A JS500 concrete mixer can make use of 4-bag cement to produce 500L concrete.
From the many experiences of workers who are working in real estate and other building projects for people in Ghana, at least 300 bags of cement will be enough to build a 3-bedroom self-contained home in Ghana.
