Concrete Calculator
Calculate concrete volume for slabs, pads, rectangular footings, walls, columns and circular forms. Use clear metric or imperial inputs, add multiple elements, then see net volume, order quantity after waste, cubic yards, cubic feet, weight, optional bag count and cost.
Project inputs
Choose one measurement system. Add separate elements when a project has different sizes or shapes.
Optional settings: waste, density, price and bag yield
How to use, formulas, worked example, FAQs & related calculators
How to Use the Concrete Calculator
Select the concrete element you are measuring, choose metric or imperial units, enter its dimensions and quantity, then add more elements when a project contains different sizes. Use the waste field only after the geometric quantities are correct.
Concrete Volume Formulas
For slabs, pads, rectangular footings and walls, ToolVault uses:
Volume = Length × Width × Depth × QuantityFor a round column or round footing:
Volume = π × (Diameter ÷ 2)² × Height × QuantityFor a circular ring or pipe form:
Volume = π ÷ 4 × (Outer Diameter² − Inner Diameter²) × Height × QuantityThe project order quantity is calculated separately:
Order volume = Net volume × (1 + Waste% ÷ 100)How Much Concrete Do I Need?
Concrete quantity is determined by the volume of the element you are filling. Convert every dimension to one internal unit system, calculate each element, add the elements together and then apply any practical waste allowance. This is why ToolVault lets you calculate multiple slabs, footings, walls and circular forms in one project.
Worked Example: Concrete Slab
Consider a slab that is 20 ft long, 30 ft wide and 4 in thick. Convert the thickness to feet: 4 ÷ 12 = 0.333333 ft.
Volume = 20 × 30 × 0.333333 = 200 ft³.
Because 1 yd³ = 27 ft³, the volume is approximately 7.407407 yd³. In metric units this is approximately 5.663369 m³.
With a 10% allowance, the order quantity becomes 220 ft³, or approximately 8.148148 yd³. Actual purchasing should follow the supplier's ordering conventions and the project's specifications.
Concrete Density and Weight
ToolVault treats density as an editable assumption because concrete density varies by mix and aggregate. The weight result is therefore:
Weight = Order volume × DensityAt an illustrative density of 2,400 kg/m³, 5.663369 m³ of concrete would correspond to about 13,592 kg before any waste allowance; the calculator applies waste before reporting its planning weight.
Concrete Bags
Packaged concrete products have product-specific yields. The calculator therefore asks for the manufacturer's published yield per bag and then divides the order volume by that yield, rounding up to a whole bag. A fixed “bag weight = fixed concrete volume” rule is not reliable across products.
Important: Quantity Is Not Mix Design
This calculator determines geometric quantity. It does not select cement, aggregate and water proportions, concrete grade, compressive strength, reinforcement, structural dimensions or code requirements. Those are separate design and specification questions.
Frequently Asked Questions
How do I calculate concrete for a slab?
Multiply slab length × width × thickness, using consistent units. Convert the resulting volume into the supplier's preferred unit, then add a practical allowance when appropriate.
How many cubic yards are in a cubic metre?
One cubic metre equals approximately 1.3079506193 cubic yards. ToolVault uses the full conversion internally and rounds the displayed result.
How much concrete should I order?
Start from the geometric volume, then add a project-appropriate allowance for waste and placement conditions. Confirm the final order quantity with the concrete supplier and project specifications.
Can I calculate footings and columns together?
Yes. Add separate elements for different shapes and dimensions, and the calculator combines their volumes into one project total.