Mulch Calculator

Mulch refers to the material placed on top of the soil in beds, tree bases, and landscapes. Organic mulches include things like wood chips, barks, shredded leaves and straw that decompose naturally. Other types of mulch include rubber and plastics that do not decompose naturally.

Mulch serves two main purposes when it comes to gardening, one aesthetic and the other practical. Visually, fresh mulch makes the beds and borders visually appealing while also playing important roles in relation to soil such as maintaining the right soil temperatures, retaining soil moisture and preventing soil erosion and weeds.

What Mulch Really Does For Your Soil

Before calculating how much mulch you’ll need, it helps to know why getting the right amount of mulch is important. In its basic definition, mulch is a covering layer for soil that does a number of things

• Protects the soil from high and low temperatures
• Helps retain moisture to reduce frequency of watering
• Prevents erosion of the top layer of soil from the effect of rainfall and wind
• Blocks sunlight that can help seeds grow into weeds
• Protects plants from soil-based plant diseases

Organic Versus Synthetic Mulch

Organic mulch (leaf mold, bark, wood chips, grass clipping) decomposes, adding to the soil fertility  although at the cost of having to be replaced more often. This will affect how often you’ll have to recalculate your mulch needs.

Synthetic mulch (rubber mulch, plastic, dyed mulch) doesn’t decompose, and therefore doesn’t enrich the soil with nutrients. Nevertheless, synthetic mulch is sold at the same price and measured in cubic feet or cubic yards like organic mulch, so the calculations remain the same.

Why Do You Need a Mulch Calculator?

Mulch is typically measured in terms of volume, either cubic feet when purchasing mulch in bags, or cubic yards for bulk mulch delivery. However, the average person thinks of his lawn in terms of square feet “My bed is around 10 feet wide by 6 feet long.” The issue here is that only using square feet will not give you the volume. It needs one more measurement depth.

Without measuring depth, you will either buy less than you should (mulch won’t be thick enough to prevent weed growth and hold moisture) or buy too much (and pay for the unnecessary mulch). This is precisely what a mulch calculator will help you with, It will convert your dimensions and depth into a volume measurement in cubic feet or yards.

How Much Mulch Do I Need

Generally speaking, landscaping professionals suggest using mulch in an amount of 2 to 4 inches, depending on the type of mulch and area to be covered:

• 2 inches – fine textured mulches or locations near delicate plants
• 3 inches – the standard depth of mulch use
• 4 inches – coarse mulch, such as wood chips or the areas where there are plenty of weeds

Using less than 2 inches of mulch would mean that weeds would still grow and soil would dry out quickly. Using more than 4 inches of mulch can result in root suffocation and too high a humidity level which can lead to rotting. Depth of mulch is the crucial element a mulch calculator requires.

Formula for Calculating Mulch Amount

Here is the formula used by all mulch calculators for rectangular areas

Length (ft) × Width (ft) × Depth (in ÷ 12) = Cubic feet of mulch needed

To calculate the required amount of mulch in cubic yards (which is the typical unit for buying bulk mulch)

Cubic feet ÷ 27 = Cubic yards of mulch needed

Mulch Calculator Example for Rectangular Areas

Imagine that you want to apply 3 inches of mulch to a garden bed that is 15 feet long and 8 feet wide

• 15 ft × 8 ft = 120 sq ft
• 3 inches ÷ 12 = 0.25 ft
• 120 sq ft × 0.25 ft = 30 cubic feet
• 30 ÷ 27 = ≈1.1 cubic yards

Formula for Circular Areas

In case when you need to cover a circular area, for example, a ring around a tree, you should use the formula for calculating the area of a circle

π × Radius² (ft) × Depth (in ÷ 12) = Cubic feet of mulch needed

Example of Mulch Calculator Calculation for a Circular Area

For example, you need to cover a circular bed with 4 feet radius with 2 inches of mulch

• 3.14 × 4² = 3.14 × 16 = ≈50.3 sq ft
• 2 inches ÷ 12 = ≈0.17 ft
• 50.3 × 0.17 = ≈8.5 cubic feet
• 8.5 ÷ 27 = ≈0.3 cubic yards

For yards that contain several garden beds of different shapes, you will need to calculate the required amounts separately and add them up, Which is what a multiple area mulch calculator does automatically.

Cubic Yards vs. Bags

Once you know your cubic footage, you’ll need to decide whether to buy bagged mulch or bulk mulch by the yard.

Standard mulch bag size

 2 cubic feet (though some brands sell 1 or 3 cubic foot bags, Always check the label)

Bags needed formula

 Total cubic feet ÷ Bag size (cu ft) = Number of bags

1 cubic yard = 27 cubic feet = about 13.5 bags of standard 2-cubic-foot mulch

Rule of thumb

 If your mulch calculator tells you that you need more than 2–3 cubic yards, bulk delivery is almost always cheaper per cubic foot than buying dozens of bags.

The mulch calculator makes the complicated calculations related to measuring square footage, changing inches to yards, and figuring out cubic feet to cubic yards, easy. You measure your garden area, choose how deep you want your mulch layer, and let the calculations give you an exact answer as to how much mulch you need to buy.