Concrete Calculator
Pouring a new patio or setting fence posts? Our free Concrete Calculator tells you exactly how many cubic yards to order or how many premixed bags to buy at the hardware store.
Concrete Calculator
What is the Concrete Calculator - Bags & Yards Needed?
The Concrete Calculator is a construction estimation tool. It calculates the three-dimensional volume of a planned concrete pour and translates that volume into standard industry purchasing units (Cubic Yards and standard 60lb/80lb bags).
How to use the Concrete Calculator - Bags & Yards Needed
- Select the shape of your pour (Slab/Square, Column/Round, or Hole).
- Enter the dimensions (Length, Width, and Thickness/Depth) in feet or inches.
- Click calculate.
- The tool outputs the total cubic yards needed and the equivalent number of premixed bags.
Example
A 10ft by 10ft patio slab that is 4 inches (0.33ft) thick: 10 × 10 × 0.33 = 33.3 cubic feet. 33.3 / 27 = 1.23 cubic yards. The tool estimates you need exactly 56 80lb bags.
Understanding Your Results
The 'Cubic Yards' number is what you use if ordering a delivery truck. The 'Bags' number is what you use if mixing it yourself in a wheelbarrow. The tool usually adds a 5% to 10% safety margin.
Common Use Cases
- DIY Patios & Sidewalks: Ensuring you don't run out of concrete halfway through finishing a backyard slab.
- Deck Construction: Calculating exactly how much concrete is needed to fill the sonotubes for deck footings.
- Budgeting: Taking the calculated bags required and multiplying by the hardware store price to estimate the project material cost.
How it Works
For a slab, the tool converts all inputs to feet and multiplies Length × Width × Thickness to get cubic feet. It divides cubic feet by 27 to get cubic yards. It then divides the cubic feet by the known yield of standard premixed bags (e.g., an 80lb bag yields about 0.60 cubic feet).
Tips & Accuracy Notes
- •Always order or buy 10% more than the exact math suggests. Ground is never perfectly level, forms bow outward, and spillage happens.
- •Mixing more than 30 bags by hand in a wheelbarrow is exhausting. Consider renting a mixer or ordering a truck for larger projects.
Frequently Asked Questions
How much does a cubic yard of concrete weigh?
A cubic yard of normal-weight concrete weighs roughly 4,000 pounds (2 tons). Ensure your truck or trailer can handle the weight before picking up bags.
What is the difference between concrete and cement?
Cement is an ingredient. Concrete is the final product. Cement is the gray powder that acts as the 'glue' to bind sand and gravel (aggregate) together with water to create concrete.
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Disclaimer: This tool provides mathematical estimates. Always consult with a local concrete supplier or structural engineer for exact requirements and load-bearing specifications.