How to Calculate How Many Bags of Concrete Are Needed for a Small Pad

Though people often use the two words interchangeably, concrete and cement are not the same. Concrete is the combination of cement, sand, crushed stone and water. You can buy the elements separately and combine them yourself or buy bags with the dry elements combined that require only the addition of water. This "premixed concrete" is commonly available in 40, 60 or 80 lb. bags. A 40 lb. bag yields approximately .3 cubic feet, a 60 lb. bag yields .45 cubic feet and an 80 lb. bag yields .6 cubic feet of concrete.

Difficulty: Easy

Instructions

Things You'll Need:

• Measuring tape
• Calculator

1. Measure the length, width and depth of the area you want to fill with concrete.

2. Multiply the length by the width and depth to calculate total cubic feet. Example: 6 feet by 4 feet by .33 feet equals 7.92 cubic feet of concrete.

3. Increase the total by five percent to allow a little extra for sinkage or waste. Example: 7.92 multiplied by 1.05 equals 8.32 cubic feet.

4. Divide the total cubic feet by the yield per bag to figure out how many bags you need. Example: 8.32 divided by .6, the yield of an 80 lb. bag, equals 14 (80 lb.) bags of concrete.

References

• "Building with Masonry"; Richard Kreh; 1998
• QUIKRETE Concrete Mix Specifications