When you start to make concrete plans for a project, there are three considerations in buying concrete. The right choice depends on the amount you will need, how many people you can muster to help and how complicated it will be to do the placement and finishing.
Concrete mixes vary in strength depending on how many sacks of cement are added per cubic yard of finished mix. The standard 5-sack mix is used for patios, walks and other structures that don’t require special engineering.

Delivered wet mixes
If your project requires a cubic yard or more of concrete, it’s best to order a delivery of ready-mixed concrete. Your site must be accessible by truck and you’ll need some help on the day of the pour.
For sites with poor access to the street, consider renting a concrete pump. This machine can be towed to the site. It pumps a special mix with more cement and smaller stone through 3-inch diameter hose and goes up stairs, up hills and under crawl spaces. Ask your supplier for this service or a recommendation for a good contractor.
Order ready-mixed concrete by the cubic yard or fraction thereof. A delivery surcharge on short orders will make ordering one or two yards quite expensive. Mixing trucks carry up to 9 yards, thus the expression, “the whole nine yards.”

Site-mixed from bulk materials
If your project requires more than about 5 cubic feet of concrete, but less than a full yard, buy the dry ingredients in bulk and mix the concrete yourself. This is also a good option if your site is inaccessible, your budget is tight, or if you just want to avoid the excitement and risks of a large pour. You can mix the concrete in a mechanically-operated concrete mixer or in a wheelbarrow.
To make a cubic yard of standard concrete mix will require five 94-pound bags of portland cement, about 17 cubic feet of sand, 19 cubic feet of gravel, and 25-30 gallons of water. Portland cement is also available in 47 pound bags from some retailers. Easier still, buy pre-mixed aggregate - sand and gravel blended for concrete. One yard of concrete will require about 2 tons of aggregate.
The Concrete Calculator does not estimate the individual components you’d need if you mix the concrete yourself, but you can ask the supplier to provide you with the right components based on a volume in cubic yards.

Ready-mix in bags
For small jobs, the best choice is dry concrete ready-mix, available in 60- or 90-pound bags. You need only add water to the mix. The 90-pound bag makes approximately 2/3 of a cubic foot of concrete. Sixty pound bags are far easier to carry and yield ½ of a cubic foot.
Some suppliers also carry a weaker, less expensive mix for setting fence posts, and a crack-resistant, fiber-reinforced mix. Using the dry, ready-mix bags is great for small quantities, though it is about twice as expensive as buying the ingredients in bulk.

Tips for Pouring
A delivery of concrete should not be undertaken lightly. It requires careful preparation and planning. Once a truck arrives, you have only so much time before the mix becomes too hard to work. Ready-mix suppliers charge for waiting time above a minimum.
Consider your site and any potential problems regarding access to your yard, such as slope, culverts and low wires. Discuss these with the dispatcher when you order. Some trucks come equipped to pump concrete several hundred feet. Be prepared with wheelbarrows and chutes to move the concrete quickly.
Make sure that all form-building and preparations are complete before the day of the pour and that enough helpers are there ahead of time.

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