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Concrete Calculator

How Much Concrete Do I Need?


From slabs and walls to steps or stairs angles, our handy concrete quantity calculator makes it quick and easy to calculate how much concrete you’ll need for your project.

For technical guidance, please refer to the step-by-step user guide below the calculator. You’ll also find a series of helpful guides below that showing you how to calculate how much concrete you’ll need for various profile types if you’d prefer to calculate these manually.

Concrete Volume Calculator:
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toolcrowd concrete calculator profile image
Please enter all dimensions above.
Disclaimer: The weights, volumes, and quantities shown in the above calculator are for guidance only and should not form the basis of any calculations where precise or accurate information is required. It isn’t uncommon for theoretical material weights and densities to vary considerably from actual weights and densities, for example, due to differences in manufacturing processes and material compositions. Therefore, you should obtain relevant, accurate information from manufacturers if exact weight, volume, and quantity calculations are required.

How to Use the Concrete Calculator

  1. Use the ‘Select a Concrete Profile’ dropdown to choose the profile type of the concrete that you’d like to calculate the quantity for.

  2. Use the ‘Concrete Type’ dropdown in box (2) to choose the type of concrete for your calculation, with normal concrete, lightweight concrete, and heavyweight concrete being available. You can also choose custom concrete if there’s a specific type of concrete you’d prefer to use.

    If you’re unsure which type of concrete to choose, we’d recommend choosing ‘Normal Concrete’ for your calculation.

    The ‘Density’ box will automatically be populated based on the type of concrete you choose. You can update the ‘Density’ figure if needed should you have a specific value that you’d prefer to use for your chosen concrete.

  3. Depending on the concrete profile chosen, you’ll need to enter various dimensions, for example, ‘Length’, ‘Width’, ‘Diameter’, ‘Thickness’, or ‘Height’.

    The calculator will automatically reformat depending on the concrete profile type chosen, meaning only the relevant dimensions will be shown.

    You can select the relevant units for each measurement using the ‘Unit’ dropdowns.

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    Note: If you choose ‘inch’ as a unit, you’ll need to use either whole or decimal numbers instead of fractions. For example, 0.25 instead of 1/4.

  4. Use the ‘Quantity’ box to specify how many units you’d like to include in the calculation.
  5. Use the ‘Calculate’ button to complete the calculation, and the ‘Reset’ button to reset the concrete calculator.

How to Calculate How Much Concrete Is Needed

Don’t feel like using the concrete calculator above? Here’s how to manually calculate how much concrete is needed for various popular shapes and profiles:

How to Calculate How Much Concrete Is Needed for a Square Slab

The first step is to determine the volume of the square concrete slab, with the equation as follows:

V = L x W x T

concrete calculator example image - square slab dimension example

When calculating the weight of steel sheet stock, the equation consists of the following elements:

V = Volume

L = The length of the square slab

W = The width of the square slab

T = The square slab’s thickness

Let’s work through an example of a shed base that has a length of 2m, a width of 2m, and a thickness of 200mm.

Because we’re using a density of 2400 kg/m3 for the calculation, we’ll need to convert the dimensions in this example to meters. The length and width of the slab are already in meters, so we don’t need to change these, but the 200mm thickness should be 0.2 (the width dimension converted to meters).

Here’s how the calculation works:

Volume = 2 x 2 x 0.2
Volume = 0.8m3

General Concrete Density = 2400 kg/m3

If we multiply the 0.8m3 volume figure by the 2400 kg/m3 density figure, we find that the total weight of concrete needed for the shed base’s square slab is 1,920 kg or 4,232.96 lbs.

How to Calculate How Much Concrete Is Needed for a Round Slab

As above, the first step is to figure out the volume of the round slab, and we can do so using the following equation:

V = 1/4 x π x D2 x T

concrete calculator example image - round slab dimension example

When calculating the volume of a round concrete slab, the equation consists of the following elements:

V = Volume

π = Pi, or 3.142

D = The diameter of the round slab, squared

T = The thickness of the square slab

Let’s work through an example of a round slab that has a diameter of 2m and a thickness of 200mm.

In this case, we’ll be multiplying 1/4 (i.e. 0.25) by the Pi figure (3.142) by the diameter squared (2m in this example), and finally, we’ll be multiplying this by the thickness of the round slab (200mm).

Because we’re using a density of 2400 kg/m3 (the general density of concrete that we’ve chosen) for the calculation, we’ll need to convert the dimensions in this example to meters.

The diameter of the round slab is already 2-meters, so we don’t need to change this, but the 200mm thickness should be 0.2 (the depth dimension converted to meters).

Here’s how the calculation works:

Volume = 0.25 x 3.142 x (2 x 2) x 0.2
Volume = 0.6284m3

General Concrete Density = 2400 kg/m3

If we multiply the 0.6284m3 volume figure by the 2400 kg/m3 density figure, we find that the total weight of concrete needed for the round slab is 1,508.16 kg or 3,324.99 lbs.

How to Calculate How Much Concrete Is Needed for a Wall

You’ll first need to calculate the volume of the concrete wall using the following equation:

V = L x W x H

concrete calculator example image - wall dimension example

Here’s a summary of the various elements of the equation:

V = Volume

L = The length of the wall

W = The width or thickness of the wall

H = The wall’s height

Let’s work through an example of a wall with the following attributes:

  • Length – 6m
  • Width – 200mm
  • Height – 1m

As with the other example calculations here, we’ll assume a density of 2400 kg/m3 for the calculation, and so we’ll need to ensure that all of our dimensions are in meters. The length and height are already in meters, but the 200mm width needs to be 0.2 for the calculation (the 200mm width dimension converted to meters).

Here’s how the calculation works:

Volume = 6 x 0.2 x 1
Volume = 1.2m3

General Concrete Density = 2400 kg/m3

If we multiply the 1.2m3 volume figure by the 2400 kg/m3 density figure, we find that the total weight of concrete needed for the wall is 2,880 kg or 6,349.44 lbs.

How to Calculate How Much Concrete Is Needed for a Hole

To figure out how much concrete is required to fill a hole, we first need to work out the hole’s volume using the following equation:

V = 1/4 x π x D2 x De

concrete calculator example image - hole dimension example

The above equation consists of the following elements:

V = Volume

π = Pi, or 3.142

D = The diameter of the hole, squared

De = The hole’s depth

Let’s work through an example of a fence post hole that has a diameter diameter of 500mm and a depth of 500mm.

In this case, we’ll be multiplying 1/4 (i.e. 0.25) by the Pi figure (3.142) by the diameter squared (500mm in this example), and finally, we’ll be multiplying this by the depth of the fence post hole (500mm).

Because we’re using a density of 2400 kg/m3 (the general density of concrete that we’ve chosen) for the calculation, we’ll need to convert the dimensions in this example to meters.

Both the diameter and the depth of the hole are therefore 0.5m (the 500mm diameter and depth dimensions converted to meters).

Here’s how the calculation works:

Volume = 0.25 x 3.142 x (0.5 x 0.5) x 0.5
Volume = 0.0981875m3

General Concrete Density = 2400 kg/m3

If we multiply the 0.0981875m3 volume figure by the 2400 kg/m3 density figure, we find that the total weight of concrete needed for the fence post hole is 235.65 kg or 519.53 lbs.

How to Calculate How Much Concrete Is Needed for Stairs

You’ll first need to calculate the volume of the concrete steps/stairs using the following equation:

V = (((SRi * SQ) * (SRu * (SQ – 1)) / 2) + ((SRi * SQ) * PD)) * W

concrete calculator example image - stair dimension example

Here’s a summary of the various elements of the equation:

V = Volume

SRi = The height of the rise

SRu = The depth of the run

SQ = The number of stairs

PD = The depth of the platform

W = The width of the stairs

Let’s work through an example of a wall with the following attributes:

  • Rise – 150mm
  • Run – 250mm
  • Number of Stairs – 5
  • Platform Depth – 500mm
  • Width of Stairs – 1m

As with the other example calculations here, we’ll assume a density of 2400 kg/m3 for our concrete, and so we’ll need to ensure that all of our dimensions are in meters. The width of the stairs is already in meters (1m), but the 150mm rise becomes 0.150m, the run becomes 0.250m, and the platform depth becomes 0.5m when converted from millimeters to meters.

Here’s how the calculation works when we input the dimensions from our example:

Volume = (((SRi * SQ) * (SRu * (SQ – 1)) / 2) + ((SRi * SQ) * PD)) * W
Volume = (((0.150 * 5) * (0.250 * (5 – 1)) / 2) + ((0.150 * 5) * 0.5)) * 1
Volume = 0.75m3

General Concrete Density = 2400 kg/m3

If we multiply the 0.75m3 volume figure by the 2400 kg/m3 density figure, we find that the total weight of concrete needed for the stairs is 1,800 kg or 3,968.40 lbs.


Quick Reference Information – How Many Bags of Concrete Do I Need?

How Many Bags of Concrete in a Yard

A cubic yard is equivalent to 27 cubic feet. Assuming a typical concrete density of 150 lb/ft3, a total of 4050 lbs of concrete would be required for a cubic yard, which equates to 101.25 x 40lb bags, 67.50 x 60lb bags, or 50.63 x 80lb bags.

How Many Bags of Concrete in a Cubic Foot

Assuming a typical concrete density of 150 lb/ft3, a total of 150 lbs of concrete would be required for a cubic foot, which equates to 3.75 x 40lb bags, 2.5 x 60lb bags, or 1.875 x 80lb bags.

How Many Bags of Concrete in a Cubic Meter

Assuming a typical concrete density of 2400 kg/m3, a total of 2,400 kilograms of concrete would be required for a cubic meter, which equates to 120 x 20kg bags, 96 x 25kg bags, 80 x 30kg bags, or 60 x 40kg bags.


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