Quick answer
Concrete Cubic Yards Calculator: direct answer
Concrete Cubic Yards Calculator helps you convert concrete project dimensions into cubic yards for ready-mix ordering and material planning. It is best for ready-mix planning and cubic-yard order estimates and returns cubic feet, cubic yards, whole bag count for material planning.
Use this calculator when you know project shape such as slab, wall, footing, or post hole, length, width, thickness, height, depth, or diameter, quantity when the same shape repeats. The estimate uses this rule: cubic yards = cubic feet / 27.
Inputs
- Project shape such as slab, wall, footing, or post hole
- Length, width, thickness, height, depth, or diameter
- Quantity when the same shape repeats
- Waste percentage
- Bag size, bag cost, and ready-mix cost when pricing is needed
Outputs
- Cubic feet
- Cubic yards
- Whole bag count
- Estimated material weight
- Estimated material cost
Formula
How this estimate works
cubic yards = cubic feet / 27
In plain terms, calculate the concrete volume from the shape dimensions, convert cubic feet into cubic yards, then add waste before comparing ready-mix and bagged options.
A 30 ft by 12 ft slab at 5 in thick with 10% waste needs about 6.11 cubic yards.
Use cases
When to use this calculator
Calculate cubic yards before requesting prices from local concrete suppliers.
Use the matching shape to convert different concrete project types into cubic yards.
Compare cubic yards with bag counts when deciding between ready-mix and bagged concrete.
Worked example
Convert slab dimensions into a ready-mix order
Ready-mix suppliers usually quote concrete by cubic yard, so this page focuses on turning project dimensions into that ordering number.
- Enter length, width, and thickness or choose the correct project shape.
- Review cubic feet first, then use cubic yards for supplier conversations.
- Round according to local supplier minimums and add waste before ordering.
Why concrete is ordered by cubic yard
Ready-mix concrete is usually ordered by volume. After calculating cubic feet, divide by 27 because one cubic yard contains 27 cubic feet.
Rounding cubic yards
Suppliers may have minimum orders or rounding rules. Use the calculator result as a planning number, then confirm ordering increments locally.
Measurement tips for a better estimate
- Convert all dimensions to the units expected by each field before calculating.
- Include thickened areas, steps, or grade beams as separate estimates when needed.
- Ask the supplier how they round small orders and whether short-load fees apply.
Common estimating mistakes
- Forgetting that one cubic yard equals 27 cubic feet.
- Ordering the exact calculated cubic yards with no waste allowance.
- Combining different project shapes into one rough rectangle and losing accuracy.
Assumptions used
- Normal-weight concrete is estimated at 150 lb per cubic foot.
- Premix bag yield is estimated from common 40, 50, 60, and 80 lb bag sizes.
- Waste factor is applied after the base volume is calculated.
Before you order materials
- Ask suppliers about minimum orders and rounding increments.
- Include waste before placing an order.
- Confirm access, delivery timing, and placement method.
Frequently asked questions
How do I convert cubic feet to cubic yards?
Divide cubic feet by 27 because one cubic yard contains 27 cubic feet. This is the standard conversion used for ready-mix planning.
Should I round up cubic yards?
Usually yes. Running short during a pour is costly, so many projects include 5% to 10% extra.
Does this work for walls and footings?
Yes. Select the matching shape and enter the relevant dimensions.