Every DIYer has experienced the frustration of making repeated trips to the home improvement store or garden center because they need more – more paint, more wood, more seed and, yes, more mulch for their landscaping beds.
We can help with the mulch part. It’s a simple matter of measuring each bed’s length and width for square footage, then deciding on your desired depth (typically 2 to 3 inches). You convert these measurements to cubic yards or bags and add a little extra to account for uneven terrain and settling.
This article will explain how to calculate your mulch needs, and we even offer a super easy mulch calculator for those who believe, like I do, that math is best left to mathematicians.
How mulch is sold
Typically, the bagged mulch you get from garden centers and home improvement stores is measured in cubic feet. Some nurseries sell larger bulk quantities by the cubic yard.
Bulk mulch
Buying mulch in bulk is generally more cost effective, especially if you’re tackling a big landscaping project. It’s typically sold in cubic yards (a cubic yard is 27 cubic feet) and is about 35% cheaper than bagged mulch.
To convert cubic yards to cubic feet, multiply the cubic yards by 27. For example: 0.5 cubic yards x 27 = 13.5 cubic feet. Or 2 cubic yards x 27 + 54 cubic feet.
Bagged mulch
Bagged mulch is great for small landscaping projects, such as mulching a flower bed, garden, or small patio. It’s sold in cubic feet, often in standard 2-cubic-foot bags.
To convert bagged mulch into cubic yards, simply divide the total cubic feet by 27 (since 1 cubic yard = 27 cubic feet). So, 20 cubic feet of bagged mulch divided by 27 equals 0.74 cubic yards (or 1 cubic yard rounded up).
Step 1: Measure your space
Rectangular bed
Take the length and width of the area and multiply these two numbers.
Example: A garden bed that is 5 feet by 10 feet has an area of 50 square feet (5 x 10 = 50).
Square bed
Since all four sides of a square are equal, measure one side and square it (or multiply it by itself).
Example: If each side is 5 feet, you get 25 square feet (5 x 5 = 25).
Circular bed
Use the formula πr² (pi times the radius squared), where pi = 3.14.
In simple terms, stand in the middle of the circle and measure how far it is to the edge. That’s your radius.
Example: A circle with a radius of 5 feet has an area of approximately 78.5 square feet (3.14 x 5² = 78.5).
Irregular shaped beds
For irregularly shaped areas, break the space into smaller rectangular or circular sections, calculate each area, and then add them up to get the total area.
Step 2: Determine mulch depth
In new beds and vegetable gardens: You need 2 to 3 inches of mulch to help retain moisture, improve airflow, and keep pesky weeds out. Worth noting is that “weeds that practically need a stick of dynamite to be removed in tight soil can usually be easily plucked in a well mulched bed,” says Norman Winter, horticulturist at Central Mississippi Research & Extension Center.
In existing beds: If you’re refreshing existing mulch, just add 1 to 2 inches to keep it effective.
Around trees and shrubs: Spread 2 to 4 inches of mulch to help them grow strong and healthy. Try to avoid volcano mulching, or piling mulch too high up the trunk or stem. It can cause root rot, pest issues, poor airflow, and even trunk damage. For trees, leave a 3 to 6-inch gap around the base. For shrubs and smaller plants, mulch 3 to 4 inches from the stem.
Read more:
Step 3: Plug data into our mulch calculator
Sure, you COULD use paper and pencil to figure out how much mulch you need for your landscaping beds. But this handy calculator will give you the same result without taxing your No. 2 pencil and wearing out your eraser.
Mulch Calculator
Quick Mulching Tips
DON’T
- ❌ Pile mulch against tree trunks. This can cause bark rot and invite pests.
- ❌ Pile mulch against your house foundation
- ❌ Till carbon-rich mulch (e.g. sawdust) into the soil, it can tie up nitrogen.
DO
- ✓ Remove weeds before applying mulch
- ✓ Keep mulch 2-3 inches away from plant stems and 3-4 inches away from tree trunks
- ✓ Refresh mulch when it starts to decompose, usually annually.
Mulch quantity quick guide
If you want a ballpark-type estimate, here’s a quick reference for how much mulch you need for a given space. These numbers assume a mulch depth of 2 inches:
| Area in square feet | Mulch in cubic feet / No. of 2-cubic-foot bags | Mulch in cubic yards |
| 50 | 8.34 cubic feet/5 bags | .31 cubic yards |
| 500 | 83.35 cubic feet/42 bags | 3 cubic yards |
| 1000 | 166.7 cubic feet/84 bags | 6.2 cubic yards |
| 2000 | 333.4 cubic feet/167 bags | 12.4 cubic yards |
Common mistakes to avoid when calculating mulch
Calculating mulch isn’t always straightforward, and there are a few common errors you could make.
Not considering existing mulch
Before you grab fresh mulch, look at what’s already in your yard. If it’s still in decent shape (not too compacted or broken down), you won’t have to clear everything out and start over. Simply add a 1 to 2-inch layer of new mulch on top to give your landscaping a clean, refreshed look.
When you crunch the numbers, you’ll need just over half the mulch you’d use for a new project.
Different types of mulch and compaction
Not all mulch types settle the same way over time. Shredded leaves and straw are light and airy, so they mat down quickly as they decompose. When this happens, you have to replenish the pile to keep it effective.
Wood chips and bark mulch are chunkier than shredded leaves, so they resist compaction better and last longer. Ultimately, with bigger pieces, you get less compaction and use less mulch. This cuts down on store visits, saving you time, money, and effort.
Read more about mulch:
Get a local pro’s help
Mulching can keep your garden looking great, but if you’d rather skip the DIY, there are other options. Whether you need advice or a helping hand, Lawn Love can connect you with a local gardening expert to help you get it just right. Plus, they can mow, aerate, overseed, and fertilize your lawn to perfection.
Sources:
“Calculate Mulch, Soil Needs for Plant Beds.” By Norman Winter, horticulturist. Central Mississippi Research & Extension Center – Mississippi State University.
“How Much Compost, Soil or Mulch?” Published by the Texas A&M AgriLife Extension – Extension Education in Travis County.
“Mulch Calculator.” Published by CalculatorSoup Online Calculators.
“Mulch Calculator – How much mulch you need.” Published by Build Wise Calculator.
Main Photo Credit: tab62 | Adobe Stock Free | License, overlay using Canva Pro
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