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DIY Potting Mix: Is It Really Cheaper to Make Your Own Soil?

You might have heard through the grapevine that making your own soil is cheaper than buying it. But are you sure if that’s always true? 

As it turns out, the answer for you depends on a number of factors. Here’s what I found:

Making your own soil is cheaper only if you buy your ingredients in quantities large enough to make upwards of 3-6 cubic feet of soil. When the quantity of desired soil mix drops to 16 quarts or less, the price per quart of premade potting mix becomes the cheaper option.

To better understand how we came to that conclusion, let me walk you through some actual price data on soil ingredients and premade potting mixes.

How Much Does It Cost to Make Your Own Soil?

Let’s first answer the question you probably came here for: how much does DIY soil cost dollar-wise?

The short answer is you should expect to spend somewhere between $0.59-$1.66/Qt depending on whether you buy large or small volume products (big bag or small bag of ingredients). The larger you go, the bigger the savings per Qt.

Before we jump into the details, let me make an assumption: you’re probably not looking to ship a pallet of ingredients to make soil for your 400 acre farm. I’m guessing you’re just looking for a small/decent sized batch of soil for your backyard garden/indoor plants. 

Here’s what I found searching Amazon for common soil mix ingredients. In my experience, you can find comparable, maybe $1-4 cheaper prices going to your local gardening store.

All prices are as of Jan 2023 (If you’re reading this from the future: I hope inflation hasn’t been too bad).

IngredientCost for a small/decent-sized, reasonably priced bagCost for the most-reviewed product online as of Jan 2023Cost/unit measurement if bought in larger volume (if available)
Perlite$10-15, 8 Qt$10.76, 8 Qt$0.33/Qt
Vermiculite$13-20, 8 Qt$14.50, 8 Qt$0.48/Qt
Horticultural Sand$8-10, 5lb$7.48, 5 lb$1.50/lb
Coco Coir$15-20, 10lb/5kg$21.59 10 lb$2.00/lb
Peat Moss$13-18, 8 Qt$15.80, 10 Qt$0.72/Qt
Compost$15-22, 4-10 lb$22.00, 10 lb$1.00/lb
Garden Soil$5-7, 22 Qt$4.57, 22.4 Qt$0.15/Qt
Worm Castings$13-17, 3-5 lb$16.42, 4.5 lb$1.13/lb

We can roughly estimate the cost/Qt by assuming we will follow a basic mix recipe like this:

The “part” means how much in proportion to the other ingredients. To make our calculations easier, we can assume 1 part = 1 Qt. For our purposes, we can roughly equate 1lb to 1.5 Qt just to get some ballpark cost estimates.

If you’re following a more complicated recipe, the price should be about the same (assuming 24K gold flakes aren’t one of the ingredients). The dollars will just be averaged out across more ingredients leading us to about the same price.

Crunching the Numbers for Homemade Soil

If we are going to buy ingredients in larger quantities, here’s a breakdown of the cost per ingredient:

Adding up the numbers and dividing by the total number of Qts, we end up with $0.59/Qt of homemade soil mix using larger-volume products. What this means is that on average, every Qt of homemade soil mix you make will cost about $0.59.

The total cost to do this from scratch with larger-volume products is $184.27 not including tax.

This would give you 192 Qt (6.4 Cubic Ft) of potting mix before running out of compost, leaving you with 13 Qt (8.7 lb) of worm castings, 50 Qt of peat moss, and 56 Qt of perlite leftover. That’s probably a good amount if you’re looking to fill up a raised garden bed.

We can also run the same calculations assuming you’re just going to buy a small bag of ingredients (which will give us a higher cost per quart). To make things simple, I’m going to pick out use a single product for each ingredient according to what has the most reviews on Amazon.

Using these numbers, we end up with $1.66/Qt of homemade soil mix using smaller-volume products

The total cost to do this from scratch with smaller-volume products is $64.98 not including tax. 

This would give you about 16 Qt of potting mix before running out of peat moss and perlite, leaving you with 2.75 Qt (1.83 lb) of worm castings and 11 Qt (7.33 lb) of compost leftover. It’s about enough to almost fill a 5 gallon bucket.

I was actually really surprised to see the cost that high. If you take a peek below at the costs for pre-made potting mix ($1/Qt even when looking at smaller-quantity bags), it’s quite a bit higher. 

Part of the reason for the high cost has to do with shipping. On Amazon, shipping costs are usually included in the price, which is about $4 per item.

If we run the numbers after taking out $4 in shipping costs, we get $1.18/Qt of homemade soil mix using smaller-volume products minus $4 shipping per item. Still higher, but at least it seems comparable to the cost of pre-made potting mix.

Now let’s take a look at what it costs to buy some potting mix.

Is It Cheaper to Buy Premade Potting Mix?

Here’s what I found searching for pre-made potting mix on Amazon:

Type of MixCost for a small/decent-sized, reasonably priced bagCost for the most-reviewed product online as of Jan 2023Cost/unit measurement if bought in larger quantity (if available)
General Purpose Potting Mix$6, 6 Qt$5.98, 6 Qt$0.75/Qt
Succulent Potting Mix$11-20, 4-10 Qt$10.98, 8 Qt$1.38/Qt
Orchid Potting Mix$6, 8 Qt$5.79, 8 Qt$0.75/Qt

At a quick glance, we can see that store-bought potting mix generally costs between $0.75-$1.00/Qt. Succulent soil is a little more expensive at $1.38/Qt.

If we compare that number with DIY potting mix prices, we find that store-bought potting mix is comparably priced with DIY soil mixes. However, there is a clear cheaper option depending on our circumstances:

What you’re looking forIs store-bought or homemade potting mix cheaper?How much cheaper is it?
Potting mix for indoor plants in small quantitiesStore-bought$0.43 – $0.91/Qt
Potting mix for a big backyard garden or long-term useHomemade$0.16/Qt
Succulent soil bought online delivered to my homeStore-bought$0.28/Qt
I only have a budget of $10Store-bought$59 total

Generally speaking, store-bought potting mix is going to be a little bit cheaper in most circumstances. The one exception is if you’re going to make a large batch of soil.

Mixing your own 192 Qt batch of soil would save you $30.72 for a batch of 192 Qt of soil. That’s pretty sizeable in comparison to the $113.28 dollars you would be spending (discounting the leftover ingredients).

If you’re like me, I was a bit surprised to see homemade potting mix costing more than store-bought. You would think that having a “do it yourself” mentality would usually save you money. 

But if you think a little deeper about it, the producers of these commercial potting mixes have an extremely efficient, large-scale process to make potting mix from ingredients bought in bulk for low prices per unit (think by the truckload).

They’re also “doing it themselves”, but on a much larger scale than you. That’s why commercial potting mix prices can be so low.

Bottom line is, considering all the market forces out there, making your own soil will only be cheaper if you buy your ingredients in large quantity.

But before you jump to any conclusions about which one you should choose, let’s compare the two other non-monetary costs: the quality of your soil and your time.

Will Homemade Soil Give You Better Quality Soil?

One of the main advantages of making homemade soil is that you have full control over the ingredients that go into the mix. What that means for you is that you can cater the mix ingredients to fit the exact needs of your particular plants

The world is your oyster when it comes to customizing your soil mix. Are you finding that your mix compacts easily? Add some more perlite next time. Do your plants seem to not be growing? Maybe add some more nutrients or compost to the soil.

Using a store-bought potting mix will probably be okay for your plants, but there’s no guarantee that the potting mix will be the absolute best option for your particular plants. It’s made to appeal to a broad audience after all, each with different needs.

You also won’t know exactly what the producers put into their mix, other than what’s on the bag’s description. Could they be adding some preservatives? Pesticides? Hard to say.

The only downside I can see with making your own soil in terms of quality is that there’s some risk that you don’t know what you’re doing and make a bad potting mix. With a store-bought potting mix, there’s not much room for error. Just use it as is, no assembly required.

Making a mistake by mixing your own soil might be a negative in the short term, but at the same time, you will also build knowledge over time as you learn from your mistakes. If you’re in it for the long haul, mixing your own soil can help you gain a deeper understanding of what exactly is needed for a plant to grow.

Will Making Your Own Soil Take A Lot Of Time?

This may or may not be a big selling point for you, but buying potting mix from the store is by far the quickest, least time-intensive option. There’s only one item that you need to get from the store and you’re done.

On the other hand, making DIY soil mix will take some effort, especially if it’s your first time making your own soil mix. 

There’s the time needed to research the best ingredients and the best proportions. There’s also the time needed to find a place to perform the mixing, measure out your proportions, mix your soil together, and store your soil mix.

If you’re like me, that could take a while. To add the cherry on top, if it turns out your mix is bad, you’re going to have to redo all of that. (That’s why it can be a good idea to test a little batch first before going all in).

If you’re a beginner to gardening and just want to get started, buying premade potting mix is a solid choice. Premade potting mix can be a good way to just test the waters and see if growing plants is something you want to devote more time to.

If you’re a crazy busy person or just don’t want to spend much time researching, maybe it might not be worth your time to do all the research to find the absolute best soil for your plants. You might be fine with using a soil that’s “good enough”. 

On the other side of the coin, you might spend more time mixing soil, but at least it’s going to be a fun time.

Should You Make Your Own Soil or Just Buy It Premade?

Considering all the factors, my personal recommendation for most people would be to make your own soil if cost isn’t much of a concern.

Looking at the cost comparison, there actually isn’t that much of a discrepancy between homemade or premade soil mixes. While the cost per Qt for homemade mixes is more expensive at small quantities, the total difference is only about $10 to $20 for a small batch.

I would say that’s a small price to pay for the benefits that you get in terms of soil quality and knowledge gained from making your own soil.

However, if you have a really tight budget, you could probably get by with a premade potting mix. 

If you only have a few dollars to spare, it’s going to be tough to get all the ingredients you need. From the prices I saw, the smallest quantity of each ingredient will cost you at least $10.

Hope this helps you make an informed decision!

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