How do you calculate the volume of concrete?

For rectangular shapes: Volume = Length × Width × Depth (all in feet). For cylinders: Volume = π × r² × height. Divide the result by 27 to convert cubic feet to cubic yards, or multiply by 0.0283 to get cubic meters.

What unit is concrete measured in?

In the US, concrete is measured and ordered in cubic yards (yd³). In metric countries, it is measured in cubic meters (m³). One cubic yard = 27 cubic feet = 0.765 cubic meters.

How do I convert cubic feet to cubic yards of concrete?

Divide cubic feet by 27 to get cubic yards. For example, 81 cubic feet ÷ 27 = 3 cubic yards. Since concrete is ordered by the cubic yard, always convert your measurement before calling a ready-mix supplier. The formula is: cubic yards = (length × width × depth in feet) ÷ 27.

What density should I use when calculating concrete volume?

Use 145 lb/ft³ (2,320 kg/m³) for standard normal-weight concrete — this is the value used by most ready-mix suppliers and structural engineers. Lightweight concrete uses 90–115 lb/ft³. For volume calculations only (not weight), the density does not affect the cubic yard result — density only matters when you need to know the weight of the pour.

Can I use this calculator for different concrete shapes?

Yes. The calculator handles rectangular volumes (slabs, walls, footings, pads) and cylindrical volumes (columns, sonotubes, post holes). For a rectangular shape, enter length, width, and depth. For a cylinder, enter diameter and height. Both give results in cubic yards, cubic feet, and cubic meters so you can order the right amount of concrete regardless of shape.

Why is concrete ordered by the cubic yard and not by weight or area?

Concrete is ordered by cubic yard (volume) because volume is what fills the forms you build — the quantity you actually need. Weight and area alone do not tell you how much three-dimensional space needs to be filled. One cubic yard is 27 cubic feet and weighs approximately 3,915 pounds (about 2 tons) at standard density. The cubic yard has been the standard US ordering unit for ready-mix concrete since the early 20th century and aligns with the way batch plants measure and price their product.

How does waste factor affect my concrete order?

A 10% waste factor is standard for most concrete pours. Waste comes from: over-excavated or uneven subgrade that requires extra concrete to fill; slightly out-of-square or bowed forms; spillage during placement; and extra concrete needed at construction joints. It is always better to have a small surplus than to run short mid-pour — adding a cold joint (pouring fresh concrete onto partially set concrete) creates a structural weak point. If you are running very short, add water to slow the set and call your supplier immediately for an emergency partial load.

Concrete Volume Calculator — Cubic Yards, Feet & Meters

What Is Concrete Volume and Why Does It Matter?

A concrete volume calculator determines the three-dimensional space that needs to be filled with concrete for a given element — a slab, wall, column, footing, or step. Calculating the correct volume is the essential first step for any concrete project because it determines how much concrete to order. Under-ordering causes a disruptive mid-pour concrete shortage; over-ordering wastes money at $130–$165 per cubic yard.

In the US, concrete is ordered in cubic yards (yd³) from ready-mix suppliers, or in individual bag counts for small jobs. One cubic yard equals 27 cubic feet and weighs approximately 3,915 pounds (about 2 short tons) at standard density of 145 lb/ft³. Always add a 10% waste factor to account for uneven subgrade, slightly out-of-square forms, and spillage.

How to Use This Concrete Volume Calculator

This concrete volume calculator handles two common concrete shapes: rectangular slabs, walls, and pads, and cylindrical columns or sonotubes. Enter your dimensions in the appropriate calculator above to get the volume in cubic yards, cubic feet, and cubic meters, plus the number of bags required. For a broader tool that includes cost and bag estimates across more shapes, see our concrete calculator.

Concrete Volume Formulas Explained

Rectangular Shape (Slab, Wall, Pad, Footing)

Volume (ft³) = Length (ft) × Width (ft) × Depth (ft)

Convert thickness from inches to feet by dividing by 12. Then divide the cubic-foot result by 27 to get cubic yards, or multiply by 0.0283 to get cubic meters.

Cylindrical Shape (Column, Sonotube, Post Hole)

Volume (ft³) = π × (Diameter ÷ 2)² × Height (ft)

Convert the diameter from inches to feet first, then divide by 2 to get the radius. Divide the result by 27 for cubic yards.

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Worked Examples

Example 1: Concrete Slab

A patio that is 12 ft × 16 ft × 4 inches thick: depth in feet = 4 ÷ 12 = 0.333 ft. Volume = 12 × 16 × 0.333 = 63.9 ft³ ÷ 27 = 2.37 cubic yards.

Example 2: Round Column

A sonotube that is 12 inches (1 ft) diameter and 4 feet deep: radius = 0.5 ft. Volume = π × 0.5² × 4 = 3.14 ft³ ÷ 27 = 0.116 cubic yards.

Concrete Unit Conversions

Concrete is sold and ordered by the cubic yard in the United States. Use these conversions when working with suppliers or plans in other units:

1 cubic yard = 27 cubic feet
1 cubic yard = 0.765 cubic meters
1 cubic meter = 1.308 cubic yards
1 cubic foot = 0.037 cubic yards
1 cubic meter = 35.315 cubic feet

How Much Concrete to Order

Always add a 10% waste factor to your calculated volume before ordering. Concrete can be lost to uneven subgrades, slightly out-of-square forms, and spillage. It is always better to have a small amount left over than to run short — a partially cured slab that has to be extended is a significant problem.

For projects over 1 cubic yard, ready-mix concrete delivered by truck is significantly cheaper and more consistent than mixing bags. Call your local concrete supplier with your cubic yard requirement, PSI specification, and delivery date. To estimate material cost alongside your volume, use our concrete slab calculator which includes a built-in cost estimator.

Sources & References

ACI 318-19: Building Code Requirements for Structural Concrete — American Concrete Institute
ASTM C94/C94M: Standard Specification for Ready-Mixed Concrete — ASTM International
PCA: Design and Control of Concrete Mixtures (16th Edition) — Portland Cement Association