Packaged concrete is a premixed combination of cement, sand and gravel. It is readily available at most home and garden centers and often sold in 60-pound bags. To prepare packaged concrete mix, all you have to do is add water. Determining the exact amount of water, however, is not such a simple process.
Read the Label
Each 60-pound bag of concrete clearly displays the necessary amount of water on its packaging. The amount of water is often listed in a spectrum. Carefully measure the maximum amount of water and place it into a separate container. Use a graduated container to measure out the water. Resist the urge to estimate amounts.
It is best to start with the minimum amount of water listed on the 60-pound bag of concrete's label. For hand-mixed concrete, add the water in all at once. If you use a concrete mixer, add half before you start the machine and the other half while the concrete is mixing. Mix the water in well. Keep mixing until there is no longer any dry concrete or any water puddles in the mixture.
Add More Water
The amount of water that your concrete mix requires will vary from bag to bag. Only when the minimum amount is well-mixed can you assess how much water the concrete mix will ultimately need. To make sure you have the right amount of water, make ridges in the mixed concrete. If the concrete is too thick to make ridges easily, the concrete needs more water. Add more water incrementally in small measured amounts. Mix each addition in thoroughly before adding more. Exceed the maximum amount of water listed if necessary to get the right consistency. If the ridges don't hold, the concrete is too loose. Add more concrete mix in measured amounts.
Multiplying and Dividing
You won't always need to use exactly 60 pounds of concrete mix. Do not mix more than you will use in one session. Concrete dries out quickly, and the mix will not last from project to project. If you need more or less than one 60-pound bag, you must adjust the water accordingly. Carefully measure the amount of concrete that you use. Use that fraction to determine the amount of water you will need. For example, if you only need 30 pounds of concrete, that's one-half of the total amount. Multiply your minimum and maximum water amounts by one-half to determine the amount of water you will need.