Calculating How Much Mulch or Compost You Need

So your garden’s mulch is getting thin, and you’ve decided that you want to add 2 inches of wood chips to top it up. Great! But how much mulch do you need to buy to make that happen?

You can do this using math (yuck!), or you can use these great calculators I’ve found online. I’ll show you both in case you’re an accountant or something and you like numbers.

The simple way:

Use this calculator to figure out the square footage of your garden beds. The calculator’s great because it figures out the square footage of non-rectangular beds, too.

Then, use this calculator to figure out how much mulch you need, in cubic yards for buying in bulk or in cubic feet for buying bagged mulch.

The math-geek’s way:

First, figure out the square footage of the area you want to mulch, by multiplying the length of the bed by the width. You don’t have to be perfect, so don’t worry too much about curves – I just try to mentally break the area into rectangles or squares so I can estimate. So, a 10 x 10 bed is 100 square feet.

Then multiply the square footage (100) by the thickness in inches you want to apply (2), then divide by 324 to give you the amount in cubic yards. If you want to know the amount in cubic feet, divide again by 27.

Using Landscape Mulch as a Casual Pathway

Should you buy bulk or bagged mulch?

Since most pre-bagged mulches are two cubic feet and cost about $8, and most bulk mulches (for you truck owners) come by the cubic yard which has 27 cubic feet and costs about $50, you can calculate whether the amount of mulch you need calls for a few bags or whether it’s best to find a friend with a truck and get bulk.

The cost is about $4 per cubic foot pre-bagged, $1.85 per cubic foot in bulk.

If you don’t have a truck, many suppliers will allow you to bring an empty garbage can or thick contractor trash bags and shovel your own bulk mulch into them, then they’ll eyeball how much you took and charge you the bulk price. It’s worth asking, as a bit of shoveling can reduce your mulch cost by half or two-thirds!

If you found this helpful, you may also like:

Mulching 101 – the lowdown on which mulches are the best

Soil Improvement 101 – tips on adding compost and amendments to your soil

For you pro-gardeners, a trick for getting a wheelbarrow in and out of your truck even if you’re a wimpy girl like me (check the comments for some great reader tips on this!)


2 responses to “Calculating How Much Mulch or Compost You Need”

  1. Thank you, it helped with a 26,000 square foot area, the price for bulk is worth it, but it pays to check around, because delivery and handling can be twice the amount for the bulk mulch in LA Calif.