Concrete Calculator | Slabs, Footings, Columns & Stairs

Q: How do I calculate concrete for a slab?

Use the Slab / Wall / Footing mode and multiply length × width × thickness: V = L × W × H. This also covers walls, pads, and square or rectangular footings.

Q: How do I calculate concrete for a round footing or column?

Use the Round Footing / Column mode: V = πr²h, where r is half the diameter and h is the depth or height.

Q: How many cubic feet are in a cubic yard?

There are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft). The calculator shows the result in cubic meters, cubic feet, and cubic yards at the same time.

Q: Does this calculator include concrete waste?

Yes. The Extra / Waste field adds a percentage on top of the calculated geometric volume. Both the calculated volume and the volume including extra material are shown, with the value including extra highlighted as the practical result to order.

Calculate how much concrete you need for slabs, walls, footings, columns, tubes, curbs, and stairs. Supports metric and imperial units with an optional waste allowance.

Calculate how much concrete you need for slabs, walls, footings, columns, tubes, curbs, and stairs. Pick a shape below, enter the dimensions in whichever units you prefer, and the result updates as you type — there is no calculate button.

Input

Length L

Width W

Thickness / Height H

Quantity

Gutter width Wg

Gutter / flag thickness Tf

Curb height Hc

The visible curb face above the gutter surface.

Curb depth Dc

The thickened portion below the gutter surface. Enter 0 if there is none.

Length L

Quantity

Run (per step) R

Rise (per step) Hr

Width W

Platform / landing depth Pd

Extra landing at the top, in addition to the steps. Enter 0 if there is none.

Number of risers

Quantity

Extra / waste

Covers spillage, uneven excavation, and formwork variation. 10% is a common starting point.

Concrete density

Used only for the estimated weight below. 2400 kg/m³ is a typical value for normal-weight concrete.

Premixed bag yield

The yield stated on the bag. If the bag only states a weight (common in Europe), choose kg/bag — this converts using the concrete density entered above. Used only for the bag estimate below.

Fig. 1

Result

Concrete needed incl. 10% extra

Calculated volume (no extra) -

Cubic meters (m³) -

Cubic feet (ft³) -

Cubic yards (yd³) -

Estimated weight -

Premixed bags needed -

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How to calculate concrete volume

Concrete is ordered by volume, not by area or weight, because it fills a three-dimensional space. To estimate that volume, the calculator multiplies the shape's dimensions together (length × width × height, for example), the same way you would work out the volume of any box, cylinder, or other solid. Every dimension is first converted to a single common unit internally, so it is safe to mix units — for example entering a length in meters and a thickness in millimeters for the same slab.

Concrete slab formula

For a rectangular slab, wall, pad, or square/rectangular footing:

$$V = L \times W \times H$$

where L is length, W is width, and H is thickness (or height, for a wall). Multiply by the number of identical slabs if you are pouring more than one.

Concrete column formula

For a round footing, column, or post hole:

$$V = \pi r^2 h$$

where r is the radius (half the diameter) and h is the depth or height. A circular slab uses the same formula.

Concrete tube formula

For a hollow cylinder, such as a pipe sleeve or a ring footing:

$$V = \pi (R^2 - r^2) h$$

where R is the outer radius and r is the inner radius. Leaving the inner diameter at 0 turns this into a plain solid cylinder.

How much extra concrete should I order?

Real projects often need more concrete than the pure geometric volume suggests, because of uneven excavation, spillage, formwork variation, and normal measurement tolerances. There is no single percentage that is correct for every job, so this calculator lets you choose your own extra/waste percentage instead of assuming one figure. Many contractors budget somewhere around 5–15% extra depending on the type of pour and site conditions; the default here is 10%, and you can adjust it to match your own project.

Cubic meters vs cubic yards

Ready-mix concrete is typically ordered in cubic meters (m³) in metric-measurement countries and in cubic yards (yd³) in the United States. One cubic yard equals 27 cubic feet, and one cubic meter is about 1.31 cubic yards. The calculator shows all three units together so you can quote the result in whichever unit your supplier uses.

Concrete Calculator FAQ

How do I calculate how much concrete I need?

Choose the shape that matches your pour (slab, round footing, tube, curb, or stairs), enter its dimensions, and the calculator multiplies them into a volume using the matching geometry formula. Set a quantity if you are pouring more than one identical shape, and an extra/waste percentage to cover real-world losses.

How much extra concrete should I order?

It depends on the job — uneven excavation, spillage, and formwork variation can all use up extra material. This calculator lets you set your own extra/waste percentage (10% by default) rather than assuming one number is right for every project.

How do I calculate concrete for a slab?

Use the Slab / Wall / Footing mode and multiply length × width × thickness: V = L × W × H. This also covers walls, pads, and square or rectangular footings.

How do I calculate concrete for a round footing or column?

Use the Round Footing / Column mode: V = πr²h, where r is half the diameter and h is the depth or height.

How many cubic feet are in a cubic yard?

There are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft). The calculator shows the result in cubic meters, cubic feet, and cubic yards at the same time.

Can I enter measurements in different units?

Yes. Every dimension has its own unit selector (millimeters up to yards), and each value is converted to a common unit before the volume is calculated, so it is safe to mix units on the same shape.

Does this calculator include concrete waste?

Yes. The Extra / Waste field adds a percentage on top of the calculated geometric volume. Both the calculated volume and the volume including extra material are shown, with the value including extra highlighted as the practical result to order.

How is concrete weight estimated?

By multiplying the calculated volume by a concrete density, which defaults to 2400 kg per cubic meter (a typical value for normal-weight concrete) and can be adjusted if you know the mix you are using.