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Mulch Calculator

How Much Mulch Do I Need?


Our handy mulch calculator makes it quick and easy to calculate how much mulch you’ll need for your garden project.

Whether you’re designing a square or rectangular bed, or you’re planning a more intricate design using circles, triangles, or even hexagons, our mulch calculator has you covered.

We’ve included some step-by-step guidance below the calculator if you get stuck. You’ll also find a series of helpful guides below that show you how to calculate how much mulch you’ll need for various real-life examples if you’d prefer to calculate these manually.

Mulch Calculator:
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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, material compositions, packing densities, and moisture content. Therefore, you should obtain relevant, accurate information from manufacturers if exact weight, volume, and quantity calculations are required.

How to Use the Mulch Calculator

  1. With our mulch calculator, you can calculate the volume or quantity of mulch required for various area shapes. You can choose the relevant profile for your calculation using the ‘Select a Mulch Profile’ dropdown.

    The following profile types are available via the dropdown:

    • Square
    • Rectangle
    • Circle/Round
    • Hexagon
    • Octagon
    • Triangle
  2. Use the ‘Mulch Type’ dropdown in box (2) to choose the type of mulch for your calculation, with the following types being available:

    • Garden Compost
    • Grass Clippings
    • Leaves
    • Sawdust
    • Shredded Bark
    • Straw
    • Wood Chips

    You can also choose ‘Custom Mulch’ if there’s a specific type of mulch that you’d prefer to use.

    The ‘Density’ box will automatically be populated based on the type of mulch you choose.

    You can update the ‘Density’ figure if needed, although this is based on industry guidance for each material.

    We would recommend using a custom density value, however, if you have a specific value available from the manufacturer of a type of mulch you’re planning to use.

  3. Depending on the mulch profile chosen, you’ll need to enter various dimensions, for example, ‘Length’, ‘Width’, and ‘Diameter’. You’ll also need to enter the planned ‘Mulch Depth’ value in the relevant input box.

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

    You can select the relevant units (in both metric and imperial) 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, 0.50 instead of 1/2.

  4. Use the ‘Calculate’ button to complete the calculation, and the ‘Reset’ button to reset the mulch calculator.

How to Determine How Much Mulch You Need

The easiest way to calculate how much mulch you need is by using our handy calculator above.

If you’d prefer to calculate the volume or quantity required manually, though, you can do so via the following equations:

To calculate the volume of mulch required:

Volume Required = Area Length x Area Width x Area Depth

Once you’ve calculated the volume of mulch required, you can then multiply this via the density of your chosen mulch to work out the weight of mulch required. For example:

Weight Required = Area Volume x Material Density

These equations remain the same whether you’re working with metric units like meters or imperial units like feet or yards.

Let’s look at some examples to show you step-by-step how to calculate how much mulch you need:

How Much Mulch Do I Need per Square Foot?

It’s relatively easy to calculate how much mulch you require per square foot, although you will need to know how deep you want your mulch layer to be.

For example, you’ll require more mulch per square foot for a 3-inch deep than a 2-inch deep layer.

The calculation to work out the quantity or volume required is as follows:

V = A x D

When calculating the quantity of mulch required per square foot, the equation consists of the following elements:

V = Volume

A = The area of mulch

D = The depth of mulch

Let’s work through an example of a 3″ deep layer of mulch.

The mulch area for this example is a square foot, based on a profile that is one foot in both length and width.

Because we’re working on the basis of square feet, we’ll need to convert the mulch depth (currently in inches) to feet, which you can do by dividing the inch dimension by 12 (3″ / 12 = 0.25 feet for this example).

Here’s how the calculation works:

Volume = 1 ft2 x 0.25 ft
Volume = 0.25 ft3

Therefore, you would need approximately 0.25 ft 3 to cover each square foot based on the desired mulch depth of 3-inches.

To summarise, the basic concept for finding the amount of mulch required per square foot is to multiply the square foot area by the depth measurement converted to feet. Doing so will leave you with the amount needed in cubic feet for whatever mulch application you need, from playgrounds to flower beds to garden paths.

How Much Mulch Do I Need for a Tree?

When it comes to how much mulch you need for a tree, the consensus is that a depth of 2-4 inches should be sufficient. You should also keep the mulch at least 6-inches away from the tree’s trunk and avoid building a ‘mulch volcano’ (i.e., where the mulch mounds against the tree’s bark).

On this basis, here’s how to calculate how much mulch you’ll need for around a tree, assuming you’re going to lay a round layer of mulch:

Step One

The first step is to treat the mulch layer as if it’s a solid circle, and so we’ll use the following equation to calculate the overall volume (disregarding the part we’ll leave free of mulch around the tree’s trunk for now):

V = π r2 d

While it may look complicated, the above equation is relatively simple and consists of the following elements:

V = Volume

π = Pi, or 3.142

r = The radius of the circular area of mulch, squared

d = The depth of mulch required

Let’s work through an example of a circular area of mulch that measures 6-feet across (i.e., in diameter) that has a required depth of 3-inches.

In this case, we’ll be multiplying the Pi figure (3.142) by the radius squared (3-feet for this example, or half of the diameter value), and finally, we’ll be multiplying this by the depth of mulch required (3-inches).

Because we’ll be working out our volume in cubic feet, we’ll need to convert the various dimensions in the example to feet. The diameter is already in feet, so we don’t need to change this, but the 3-inch depth should be 0.25 (the depth dimension divided by 12 to convert from inches to feet).

Here’s how the calculation works:

Overall Mulch Volume = (3.142 x (3 x 3)) x 0.25
Overall Mulch Volume = 7.070 ft3

Step Two

The second step is to calculate the volume of the hollow section of the mulch layer required around the base of the tree’s trunk, and we’ll use the same equation that we used in step one above, assuming a 6-inch gap between the tree and the mulch.

As above, we’ll need to convert the dimensions to feet to give us our final volume in cubic feet.

To suit the calculation, we’ll take the 3-inch radius (half the diameter) and convert this to 0.25 ft (the depth dimension divided by 12 to convert from inches to feet). We’ll also divide the depth by twelve to get 0.25 ft for the calculation (3-inches divided by 12 equals 0.25).

Here’s how the second part of the calculation works:

Hollow Section Volume = (3.142 x (0.25 x 0.25)) x 0.25
Hollow Section Volume = 0.049 ft3

Step Three

Next, we need to subtract the volume of the hollow section of mulch from the overall mulch area’s volume.

For example:

Total Volume = Overall Mulch Volume – Hollow Section Volume
Total Volume = 7.021 ft3

Therefore, you would need just over 7 ft3 to surround a tree with 6-feet of mulch, assuming a depth of 3-inches and a 6-inch gap around the base of the tree.


Quick Reference Information

What Is Mulch?

A mulch is a loose covering of material, for example, compost, bark, wood chips, or a sheet material used to cover the soil’s surface.

You can add mulch to both bare soil on the ground and the soil in pots and containers.

The main purpose of mulch is to help the soil retain moisture by reducing evaporation, but it also helps to improve the soil’s health by adding organic matter as the mulch breaks down. In addition, mulch can also help limit the growth of weeds by eliminating the sunlight needed by weeds to germinate and grow, and it also helps improve your garden’s appearance.

Types of Mulch

There are two main types of mulch:

  • Organic mulches that are typically biodegradable (i.e., they decompose or are broken up over time by micro-organisms), for example, garden compost, wood chips, bark, or straw.
  • Inorganic mulches that are typically non-biodegradable (i.e., they don’t decompose or break up through the actions of micro-organisms), for example, slate or shingle, or sheet materials such as woven landscape fabric.

What Are the Benefits of Mulch?

Here are some of the benefits of adding mulch to your garden:

  • Mulch can cut down on the need for watering by helping the soil retain moisture and reducing soil evaporation.
  • Mulch can reduce the need for weeding as the layer of mulch prevents weeds from getting the sunlight needed to germinate and grow.
  • Organic mulch provides nutrients and organic matter back into the soil as it breaks down, improving the soil’s health.
  • Organic mulch provides an excellent habitat for micro-organisms such as warms, which burrow through the soil, forming air and water channels that improve and enhance root growth.
  • Mulch can help insulate the soil underneath to protect the roots of plants and trees from very hot or cold temperatures.
  • You can use a mulch layer to provide a decorative finish in your garden.

How Deep Should Mulch Be?

In most cases, you should lay biodegradable mulches such as garden compost, grass clippings, wood chips, or bark to a depth of between 2-inches (5cm) and 3-inches (7.5cm) to retain moisture, keep down weeds and insulate the soil.

In general, the depth depends on how coarse the mulching material is. For example, you should keep finer mulches like hardwood mulch below 3-inches deep to allow sufficient airflow through the entire depth of the mulch. Coarser mulches, such as wood chips or shredded bark, will be less restrictive for airflow and can be laid deeper.

Aside from the potential airflow issues that can cause suffocation of a plant’s or tree’s roots, other problems can occur from an excessively thick layer of mulch. For example, when mulch is too thick, it can soak up any excess moisture before it reaches the roots of any plants or trees, preventing them from getting the water they need to thrive. Thick layers of mulch can also invite pests such as rodents.

How Much Mulch Is in a Bag?

In the United States, mulch typically comes in the following bag sizes:

  • 1 Cubic Foot
  • 2 Cubic Foot
  • 3 Cubic Foot

Here’s an approximate guide to how much coverage you can expect from each bag:

1 Cubic Foot Bag Size

1 Cubic Foot Bag Mulch Coverage

Mulch Depth Approximate Bag Coverage
1-inch 12 ft2
2-inches 6 ft2
3-inches 4 ft2
4-inches 3 ft2
2 Cubic Foot Bag Size

2 Cubic Foot Bag Mulch Coverage

Mulch Depth Approximate Bag Coverage
1-inch 24 ft2
2-inches 12 ft2
3-inches 8 ft2
4-inches 6 ft2
3 Cubic Foot Bag Size

3 Cubic Foot Bag Mulch Coverage

Mulch Depth Approximate Bag Coverage
1-inch 36 ft2
2-inches 18 ft2
3-inches 12 ft2
4-inches 9 ft2

In the UK, mulch bags typically come in liters.

Here’s how much coverage you can expect from a typical UK mulch bag size:

100 Liter Bag Size

100 Liter Bag Mulch Coverage

Mulch Depth Approximate Bag Coverage
25mm (1-inch) 4 m2
50mm (2-inches) 2 m2
75mm (3-inches) 1.33 m2
100mm (4-inches) 1 m2

How Much Mulch Is in a Yard?

Here’s an approximate guide to how much coverage you can expect from one cubic yard of mulch:

1 Cubic Yard Bag Size

1 Cubic Yard Bag Mulch Coverage

Mulch Depth Approximate Bag Coverage
1-inch 324 ft2
2-inches 162 ft2
3-inches 108 ft2
4-inches 81 ft2

How Much Does 1-Yard of Mulch Weigh?

The weight of mulch per cubic yard will vary depending on several factors, including the type of mulch, how compressed it is, and the moisture content of the mulch.

The weight per cubic yard will be higher for more compressed (i.e., packed more tightly) or wetter mulch.

Here is a summary of the average weight per cubic meter for a variety of mulch types:

1 Cubic Yard Mulch Weight

Mulch Type Average Mulch Weight Per Cubic Yard
Garden Compost 981 lbs (445 kg)
Grass Clippings 865 lbs (392 kg)
Leaves 750 lbs (340 kg)
Sawdust 606 lbs (275 kg)
Shredded Bark 981 lbs (445 kg)
Straw 923 lbs (419 kg)
Wood Chips 937 lbs (425 kg)

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