How Many Litres of Compost Are In A Tonne Bag

How Many Litres of Compost Are In A Tonne Bag?

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If you are looking at buying a lot of compost for your garden then you might have been tempted by just buying a big bulk bag, I know I have many times. But is this actually a good deal, how many litres of compost do you get in a tonne bag?

How Many Litres of Compost Are In A Tonne Bag
How Many Litres of Compost Are In A Tonne Bag

How Many Litres of Compost Are In A Tonne Bag

The weight of compost will change massively depending on how dry it is which makes it impossible to compare the two on their own.

When is a Tonne Bag Not A Tonne?

Another factor to bear in mind is that a tonne bag of compost is rarely actually a tonne. A metric tonne is 1000kg but this is not usually the case for tonne bags of compost.

What has happened is that a tonne bag has become the generic name for a big bulk bag of compost rather than meaning there is actually a 1000kg in it.

For most composts, a 1000kg would actually require a huge bag and be much bigger than the bulk bags often delivered by builders’ merchants.

Bulk Bags

This tonne bag not a tonne bag debacle actually helps us out here though if we dig deeper. if you look on most landscaping supply sites now for a bulk bag of compost you will find that they actually show the volume of compost rather than saying it is a tonne bag.

This is probably a trading standards thing I would imagine and actually helps us out as regular gardeners. This allows us to compare getting a bulk bag to buying regular compost bags and see if we actually are getting a good deal.

So it is a good deal?

This would depend on the compost and the quality of it. but if you are just looking for volume rather than quality then often bulk bags aren’t that much of a good deal.

Let’s do a little maths to work this out.

I just went on Wickes for this to make the calculations simple. Their bulk backs of compost are 730L and priced between £120 and £135 depending on the type, these prices are true at the time of writing 23/05/2022.

That works out at 16 – 18 pence per litre of compost. If we now look at bags Wickes sells a 100L bag of multi-purpose compost for £12 that’s easy to work out at 12 pence per litre. So the bagged stuff is cheaper here.

I’m not saying you can’t find a cheaper supplier of bulk compost, trust me they are out there, but they are still fairly similar in price to buying large bags. And this is before you factor in any delivery charges which can be high for the big bags.

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  1. Hi Daniel. Thanks for that. I had pretty much come to the same conclusion but it is good to have it confirmed by you. I think this especially applies if you want peat free and/or organic material. And some bulk supplies are of very questionable quality. The only plus is that you don’t have to worry about what to do with all that plastic! They say it’s recyclable but my local tip won’t have that and who washes out their used compost bags? Any tips on that?

    1. Hi Julie, I like to use them in places where you would otherwise use a plastic weed liner, so the inside of raised beds and under paths. In fact, the paths at my allotment are a hodge podge of different compost bags with a layer of wood chippings on top.

  2. Glad to see someone actually do the maths! Have you also ever checked the actual volume of compost in a shop-bought bag of compost? I just bought a so-called bargain 50L bag, tipped it into a calibrated 10L bucket – two and a half times! ie it only had 25 litres of compost in it! How many brands of compost are ever checked by weights and measures these days, I wonder?

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