Construction Calculators
Concrete Calculator
Estimate concrete in cubic yards, cubic feet, cubic meters, and bags for slabs, footings, post holes, and small pours.
Project setup
Estimate concrete for slabs, footings, round piers, post holes, and small manual-volume pours.
Waste percentage
Extra concrete helps cover spills, uneven forms, and ordering margin.
Leave blank if you only need quantities.
Assumptions
Bag yields vary by product and mix. Check the bag label or manufacturer specs for exact yield. This is a material estimate, not structural engineering advice.
Enter dimensions above to estimate concrete in cubic yards, cubic feet, cubic meters, bags, and cost. Add waste percentage for spills, uneven forms, or ordering safety margin.
Choose a mode, enter dimensions or volume, then review concrete quantity and bag estimates.
Concrete calculator formulas
Slab volume = length x width x thickness.
Footing volume = length x width x depth x number of footings.
Round column or post hole volume = pi x radius squared x height x quantity.
Cubic yards = cubic feet / 27.
Cubic meters = cubic feet / 35.3147.
Total with waste = volume x (1 + waste % / 100).
Bags needed = total cubic feet / bag yield, rounded up.
Cost = amount x selected price unit.
Worked examples
A 10 ft x 12 ft slab at 4 inches thick is 40 ft³, or 1.4815 yd³ before waste. With 10% waste, it becomes about 1.6296 yd³.
Six post holes that are 12 inches wide and 24 inches deep need about 9.42 ft³ before waste, or about 0.349 yd³.
If a project needs 9.42 ft³ and each 80 lb bag yields about 0.60 ft³, 9.42 / 0.60 = 15.7, so round up to 16 bags.
Common concrete estimate mistakes
- Entering inches as feet instead of converting depth.
- Forgetting waste or overage for spills and form variation.
- Confusing cubic feet and cubic yards when ordering.
- Not checking the bag yield printed on the product label.
- Ignoring uneven forms, excavation, or subgrade variation.
- Assuming bagged concrete is always practical for larger pours.
- Using a material calculator as structural engineering advice.
Plan nearby materials too
Concrete projects often need area, base, and fill planning. Use the Square Footage Calculator, Gravel Calculator, or Sand Calculator for related estimates.
Quick answers
What this calculator answers
- Result: Estimate concrete in cubic yards, cubic feet, cubic meters, bags, and optional cost.
- Method: Concrete volume is shape area times depth, then converted using 27 cubic feet per cubic yard.
- Bag planning: Compare common bag sizes against your project volume before choosing bagged or ready-mix concrete. concrete bags vs cubic yards guide
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Construction estimates can vary with site conditions, waste, compaction, product coverage, local requirements, and measurement accuracy. Verify material orders before purchasing.
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Choose slab, footing, round column, post hole, or manual volume mode.
Select a preset if it matches your project, then adjust dimensions and depth.
Choose bag size, waste percentage, and optional concrete price.
Review cubic yards, cubic feet, cubic meters, bag count, and cost before ordering.
Related Tools
Other helpful tools in the Construction Calculators category.
Square Footage Calculator
Calculate square footage for rooms, walls, flooring, paint, concrete, gravel, and other material planning.
Square Feet to Cubic Yards Calculator
Convert area and depth into cubic yards and cubic feet for gravel, sand, concrete, mulch, topsoil, and bulk materials.
Cubic Yard Calculator
Calculate cubic yards from length, width, and depth for gravel, sand, concrete, mulch, topsoil, fill, and other bulk materials.
Concrete Bags Calculator
Estimate how many 40 lb, 50 lb, 60 lb, 80 lb, or 90 lb concrete bags you need for slabs, footings, post holes, and small pours.
Rebar Calculator
Estimate rebar stock bars, total length, weight, and cost for simple slab grids. Material estimating only.
Gravel Calculator
Estimate gravel in cubic yards, tons, bags, and cost for driveways, paths, patios, drainage, and landscaping.
Sand Calculator
Estimate sand in cubic yards, tons, bags, and cost for pavers, patios, sandboxes, pool bases, landscaping, and fill projects.
Area Calculator
Calculate the area of any geometric shape.
Related Guides
Background reading and explanations related to Concrete Calculator.
Square Feet to Cubic Yards Explained
Learn how area and depth turn into cubic yards for gravel, sand, and concrete planning.
Concrete Bags vs Cubic Yards Explained
Understand when bag counts make sense and when cubic yards are better for concrete planning.
DIY Renovation Calculations (Estimate Materials & Costs Correctly)
Tips for measuring your space accurately.
Frequently Asked Questions
Common questions about Concrete Calculator and how to read the result.
How do I calculate how much concrete I need?
Calculate the project volume in cubic feet, divide by 27 for cubic yards, then add a waste percentage for spills, uneven forms, and ordering margin.
How many cubic yards of concrete do I need?
Cubic yards equal cubic feet divided by 27. This calculator shows the cubic yards after your selected waste percentage.
How many bags of concrete do I need?
Divide total cubic feet by the selected bag yield, then round up because partial bags cannot be purchased.
How much concrete is in a 60 lb or 80 lb bag?
This calculator assumes about 0.45 cu ft for a 60 lb bag and 0.60 cu ft for an 80 lb bag. Check the product label for exact yield.
Should I add extra concrete for waste?
Usually yes. Extra concrete helps cover spills, form variation, uneven excavation, and ordering safety margin.
When should I use ready-mix instead of bags?
For pours above about 1 cubic yard, ready-mix may be more practical than mixing many bags by hand. Supplier minimums and access still matter.
Can I use this for slabs, footings, columns, and post holes?
Yes. Choose the matching mode and use the result as a planning estimate, not structural engineering advice.