Concrete slabs
Multiply length by width by thickness, then multiply by the number of identical slabs. Slab thickness is often entered in inches while length and width are entered in feet.
Material calculator
Concrete Calculator
Calculate concrete volume, a ready-mix order quantity, and bag counts for slabs, walls, footings, and round columns using US, metric, or mixed units.
How much concrete do you need to order?
Volume, ready-mix order, and bags
Project inputs
Enter dimensions
Estimate
Concrete to order
Recommended ready-mix order
5.5yd³
4.205 m³ equivalent
Volume breakdown
Volume before waste4.94 yd³
Waste allowance0.49 yd³
Total concrete needed5.43 yd³
Recommended order5.5 yd³
Cubic feet146.67 ft³
Cubic meters4.153 m³
Estimated material cost
Enter a price per cubic yard to estimate material cost.
Pre-mixed concrete bags
40 lb bags489
60 lb bags326
80 lb bags245
Bag yields are approximate and vary by manufacturer. Check the package yield before purchasing.
How it's calculated
Slab volume
Length × width × thickness × quantity
Then add 10% waste and round the cubic-yard order upward to the next 0.25 yd³.
Method
How to calculate concrete volume
Measure each dimension, convert them to compatible units, apply the shape formula, and then add a realistic waste allowance. Keep full precision until presenting the result or selecting an ordering increment.
Concrete walls
Multiply wall length by height by thickness and quantity. Measure the concrete itself; openings and changes in wall thickness may need separate calculations.
Concrete footings
Multiply footing length by width by depth and quantity. If footing sizes vary, calculate each group separately and add the totals.
Round columns
Divide diameter by two to find the radius, then use π × radius² × height × quantity. This formula applies to solid round columns.
Waste factor
Waste adds an allowance for site variation, uneven forms, spillage, and handling. The calculator applies the selected percentage to the measured volume before ordering and bag calculations.
Ordering ready-mix
Ready-mix is commonly ordered by the cubic yard. The calculator always rounds total volume including waste upward to the next 0.25 yd³; confirm minimums and increments with your supplier.
Estimating concrete bags
Bag estimates divide total cubic feet including waste by an approximate bag yield and round up. Actual yield varies, so use the yield printed on the product you plan to buy.
Common questions
Concrete calculator FAQ
How do I calculate how much concrete I need?
Multiply the structure dimensions to find its volume, multiply by the quantity, and then add a waste allowance. For a round column, use π × radius² × height. This calculator converts every dimension to a common unit before applying those formulas.
How many cubic feet are in a cubic yard of concrete?
One cubic yard contains exactly 27 cubic feet. Divide cubic feet by 27 to convert a volume to cubic yards.
How much extra concrete should I order?
A 10% waste factor is a common planning starting point, but the right allowance depends on excavation accuracy, formwork, spillage, site access, and supplier requirements. This calculator allows 0% to 30% and then rounds the ready-mix order upward to the next 0.25 cubic yard.
How many bags of concrete do I need?
Divide the total cubic feet, including waste, by the yield printed on the bag and round up to a whole bag. The calculator uses approximate yields of 0.30 ft³ for 40 lb, 0.45 ft³ for 60 lb, and 0.60 ft³ for 80 lb bags; always verify the manufacturer’s packaging.
Should I order ready-mix concrete or use bags?
Bags can be practical for small pours and repairs, while ready-mix is often easier for larger, continuous pours. Consider total volume, mixing capacity, placement time, access, delivery minimums, and short-load charges before deciding.
Does the estimated cost include delivery and labor?
No. The estimate only multiplies the recommended rounded order by the price per cubic yard you enter. It does not include delivery, taxes, short-load fees, pumping, tools, reinforcement, formwork, or labor.
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