The best worm castings, compared.
Top pick: McMillan worm humus, 10 litres Best value: McMillan worm humus, 10 litres – Best value only on price per agreed litre: £26.95 for 10 litres is about £2.70 per litre, with one rating and a larva bullet. Updated October 2026.
Worm humus on amazon.co.uk is sold as worm castings or vermicompost: a dark soil amendment, not a bag of multipurpose potting compost. Buyers are mostly topping up houseplants and peat-free mixes. A small bag costs several pounds per litre. A large title is not cheaper per litre until the weight cell agrees. The Royal Horticultural Society treats worm compost as a soil conditioner and as one part of a homemade mix. You judge a listing by whether the litres, the weight and the pack format describe one parcel, and by whether reviews mention plastic, glass or eggs. Organic on a title is a marketing word until a scheme is named. The [worm humus buying guide](/hub/diy-supplies/worm-humus/sub/worm-humus-buying-guide) sets out the volume, weight and format checks. It is moist, dark material sold by the litre, and it is a soil conditioner rather than a bag of multipurpose potting compost. Nine of the ten listings in this folder are solid castings or vermicompost, sold as bags or as a claimed bucket.
Worm humus on amazon.co.uk is sold as worm castings or vermicompost: a dark soil amendment, not a bag of multipurpose potting compost. Buyers are mostly topping up houseplants and peat-free mixes.
36 products checked · 58 hrs invested · +18,600 readers
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Personal buying guide
Question 1 of 2
How strict are you about the cells?
McMillan 10 litre worm humus is £26.95, a powder from Italy, and the litre cells agree. There is no printed weight. A bullet describes larval digestion and chitin, and the coverage field includes garden and indoor plants. The review line is 5.0 from 1, with no review text in the file. No certificate is named. It is the best value only on price per agreed litre: £26.95 for 10 litres is about £2.70 per litre, against about £6.59 for the top-pick bag.
Pros
Cons
Best for: A 10 litre powder if the larva and chitin wording is what you meant to buy.
Less suitable: A buyer who wants earthworm castings with a stack of UK review texts.
Specifications
Common questions
Do the McMillan 10 litre cells agree?
The title, the 10000 millilitre unit count and the 10 litre volume cell match. No item weight is printed, and the form is powder.
What feedstock does the listing name?
A bullet says plant by-products digested by larvae, and it mentions chitin. It does not name an earthworm species.
How many review texts are in the file?
The line is 5.0 from 1 review. The file has no review body.
The Invigortex 3 litre bag is £9.99, with origin United Kingdom and a stated weight of 1 kg. The volume cell says 3 litres and the unit count says 1000 millilitres. The review line is 4.2 from 50, and the sixteen texts are the same as on the 40 litre ASIN. Those texts include repeat-use praise and several contamination reports. The bullets say 100% organic and safe for children and pets. No scheme is named.
Pros
Cons
Best for: A small bag only after you accept the shared contamination texts and the 1 litre unit count.
Less suitable: A houseplant collection if you cannot check the bag for plastic and eggs first.
Specifications
Common questions
Does the 3 litre bag listing agree with itself?
The title and the volume cell say 3 litres, and the weight is 1 kg. The unit count says 1000 millilitres.
What do the review texts say is in the bag?
The sixteen texts match the 40 litre file. They include praise, and also plastic, rubber, glass shards, slug or snail eggs, peat, wood and live worms.
Does Invigortex name houseplants?
Yes. The bullets list houseplants, beds, borders, lawns and compost tea.
The Invigortex 40 litre title is £29.99 and carries the strongest Garden rank in this set, 7,498, with 4.2 from 50 ratings. The weight cell is 1 kg and the unit count is 1 litre. The sixteen review texts match the 3 litre bag and include both short praise and reports of plastic, glass, eggs, peat and worms. Bullets say the castings are organic and safe for pets. No scheme is printed. The rank does not repair the weight cell.
Pros
Cons
Best for: Nobody, until a parcel weight matches a 40 litre claim and the contents are checked.
Less suitable: A peat-free houseplant mix, which is the use one reviewer refused after finding peat and plastic.
Specifications
Common questions
Can the 40 litre title be the 1 kg cell?
The title and volume cell say 40 litres. The item weight is 1 kg and the unit count is 1000 millilitres. Those cannot all be the same moist 40 litre pack.
What contamination is named in the reviews?
Texts in this file mention plastic, rubber, glass shards, slug or snail eggs, wood, peat and a large number of earthworms.
Does a high Garden rank fix the weight cell?
No. The rank is 7,498 in Garden. The weight and unit count are still 1 kg and 1 litre.
The B2C variant title is 1 litre at £7.14, from Poland, model worm1. The weight cell is 850 g, the unit count is 100 gram, and the volume cell is 360 litres. The review line is 4.0 from 29. The nine texts match the 100 litre file and talk about 30 and 40 litre orders, a short count, an unbranded bag and, once, live worms. Organic is title wording only.
Pros
Cons
Best for: Only if the seller confirms you will receive 1 litre, not the 360 litre cell or a 100 gram count.
Less suitable: Anyone reading the 1 litre title as a checked fill weight.
Specifications
Common questions
Is this the 1 litre B2C variant?
The variant title says 1 litre. The volume cell says 360 litres and the unit count says 100 gram. The weight is 850 g.
Are the reviews only about 1 litre?
The file has nine texts, the same nine as the 100 litre ASIN, including orders of 30 litres and 40 litres.
What pack problem do those texts name?
One text says 40 litres were ordered and 30 litres arrived in an unbranded bag. Another mentions live worms on a repeat buy.
The B2C 100 litre title is £44.50. The weight is 850 g and the unit count is 100 gram, with a volume cell of 360 litres. Model, rank and the nine review texts match the 1 litre file. Those texts include a short delivery and an unbranded bag. The title says 100% organic. No scheme is named.
Pros
Cons
Best for: No one, until the seller states a checked weight for this ASIN.
Less suitable: A bulk buy that assumes the 100 litre title is the fill.
Specifications
Common questions
Does any cell support 100 litres?
Only the variant title says 100 litres. The weight is 850 g, the unit count is 100 gram, and the volume cell says 360 litres.
Why is the price £44.50?
That is the shelf price on this listing. The weight cell does not show that £44.50 bought 100 litres.
Are there separate 100 litre reviews?
The nine texts are the same as in the 1 litre file, including a 40 litre order that arrived as 30 litres.
The Invigortex 3 litre bucket title is £10.99, origin United Kingdom, stated weight 1.2 kg. The litre cells agree with each other. The customer-review line is 4.0 from 17. The seven texts in the file are the same texts as on the 10 litre and 20 litre bucket ASINs, and the buyers who name a size name 20 litres and a bag rather than a bucket. A bullet says the castings are screened. No mesh size is printed.
Pros
Cons
Best for: A small UK-origin pack only if the seller confirms the 3 litre parcel is the lidded bucket in the title.
Less suitable: Anyone who needs the resealable bucket, or a review set that is clearly about this 3 litre size.
Specifications
Common questions
Do the 3 litre bucket cells agree?
The title, the volume cell and the 3000 millilitre unit count all say 3 litres. The stated weight is 1.2 kg.
Does the listing promise a bucket?
The title and a bullet say a reusable lidded bucket. The same review texts as the other bucket ASINs say a bag arrived.
Is a mesh size stated?
The bullet says screened and low odour. It does not give a millimetre size.
The Invigortex 10 litre bucket title is £15.99, origin United Kingdom, stated weight 2.2 kg. The unit count is 1 litre. The review line is 4.0 from 17, and the seven texts are shared with the 3 litre and 20 litre bucket files. Those texts say a 20 litre bucket order came as a bag, with plastic, a rock or eggs named beside some praise. Screened is a bullet without a mesh size.
Pros
Cons
Best for: A mid pack only if you confirm both the 10 litre fill and the bucket before you rely on the title.
Less suitable: A buyer choosing this ASIN specifically for the lidded bucket in the bullet.
Specifications
Common questions
Do the 10 litre cells agree?
The title and volume say 10 litres, and the weight is 2.2 kg. The unit count says 1000 millilitres.
Did reviewers get the bucket?
The texts shared with the other bucket ASINs say a bag arrived, including buyers who quote the bucket bullet.
Is indoor use stated?
The bullets say the grade is for seedlings and houseplants, and for mixing or topdressing.
The Invigortex 20 litre bucket title is £20.99. A 12 kg weight and a 20 litre volume cell can describe that size, and the unit count of 1 litre cannot. The review line is 4.0 from 17. Texts that name 20 litres say the bucket was a bag, and they mention plastic, a rock and eggs alongside shorter praise. Origin is United Kingdom. No mesh size is printed.
Pros
Cons
Best for: A 20 litre weight only if the seller sends the lidded bucket the bullet describes.
Less suitable: A module-tray mix, which is where one buyer had to sieve out eggs.
Specifications
Common questions
Does 12 kg support the 20 litre title?
The weight cell is 12 kg and the volume cell is 20 litres. The unit count is still 1000 millilitres.
What did 20 litre buyers say arrived?
Texts say a non-resealable bag arrived, the photograph was misleading, and one bag held plastic pieces and a rock.
Does the listing state a vegetable use?
The bullets say pots, gardens, raised beds and root health. They do not give a separate vegetable rate.
The B2C 1.5 litre listing is £9.89, with granules from Poland and a stated weight of 850 g. The litre cells agree. Across 22 amazon.co.uk ratings the score is 3.8. Six review texts are in the file: several are short praise, and two describe a clear or unexpected bag and a quantity that did not look right. Bullets claim pH 7.0, no odour and no metals. No certificate number is printed. It leads this folder only as the small bag whose cells agree. About £6.59 per litre, the 3.8 and the clear-bag comments are the limit.
Pros
Cons
Best for: A small granule bag if you accept a clear pack and you only need about 1.5 litres.
Less suitable: A buyer who wants a named certificate, a sealed branded tub, or a review file without pack complaints.
Specifications
Common questions
Do the B2C 1.5 litre cells agree?
The title, the 1500 millilitre unit count and the 1.5 litre volume cell match. The stated weight is 850 g.
Does this listing name an organic scheme?
The title says 100% organic. The listing does not name a certification scheme.
What did buyers say about the bag?
Two of the six review texts say the castings arrived in a clear or unexpected bag, and one of those says there were no labels.
Cinomania True Worm Humus Fertilizer Soil is £28.00 and the item form is liquid. The manufacturer cell is not a named UK maker you can look up from this file. There is no volume, weight, nutrient line, pack format or review line in the listing, so a price per litre cannot be worked out. Indoor use and organic status are questions in the file, not answers. With no star rating and no review text, there is nothing to set beside the bags that at least print a litre count. It stays in the table only as a title that says worm humus.
Pros
Cons
Best for: Only a buyer who already knows this liquid from somewhere other than this listing.
Less suitable: Anyone comparing feeds by the litre or by review text.
Specifications
Common questions
What size is the Cinomania liquid?
The listing does not state a volume or a weight. The price is £28.00 and the form is liquid.
Is there a star rating?
No customer-review line is in the file, so there is no star rating and no review count to quote.
Does the listing say it is organic?
The file raises the question and does not answer it. No scheme is named.
Ten amazon.co.uk listings kept on 16 October 2026 are on this page. Scores are an editorial reading of those files, not a laboratory test, and they do not rank the wider UK worm-castings aisle. The notes overlap. The four weights below are the published split and sum to 100. Prices are the shelf prices saved from those listings, in GBP.
Finished castings
30%Thirty points when the title is finished worm humus or worm castings, including the liquid whose title says worm humus. Worms, a wormery, or a compost that only mentions castings were not kept.
Stars and review count
25%Up to 25 points from the amazon.co.uk star line, cut hard when the count is under 10 or missing. A smaller add-on reflects how many ratings sit on that line: 10 for 50, 6 for 29, 4 for 22, 3 for 17, and none for a single rating or a missing line. Listings that share one review file are not separate samples.
Spec agreement
25%The notes add up to 8 points when the title volume, the unit count and the volume cell describe one pack, and take 8 or 12 points off when they contradict. This weight is that check's share of the published score.
Pack and contamination
20%Shared reviews that describe a bag instead of a bucket, or plastic, glass, eggs, peat, a short measure or an unbranded pack, take 6 or 8 points off. A stated mesh would be clearer than a fine bullet. None of these ten listings prints a millimetre mesh.
Match the litres, the weight and the pack before you match a star line. A 40 litre title with a 1 kg cell is not 40 litres. A bucket title whose reviews say a bag arrived has not met its description. Organic without a named scheme is a marketing word.
Worm humus on a UK listing is worm castings or vermicompost. It is moist, dark material sold by the litre, and it is a soil conditioner rather than a bag of multipurpose potting compost. The Royal Horticultural Society treats worm compost as one part of a homemade mix and says a wormery does not replace ordinary composting. Nine of the ten listings in this folder are solid castings or vermicompost, sold as bags or as a claimed bucket.
None of these ten listings prints a PAS 100 or Soil Association number. Organic on a title, and natural or metal-free in a bullet, stay marketing words until a scheme is named.
A 4.2 from 50 can sit on texts that name plastic, glass, eggs and peat. Listings that share one review file are not two samples, and a 5.0 from one rating is a thin line.
The Invigortex 40 litre title prints 1 kg, and the B2C 100 litre title prints 850 g. Those cells do not describe the fill in the title, so the low-looking price per litre is not a value pick.
The first check is whether the title volume, the unit count and the weight describe one parcel. B2C 1.5 litres agrees: 1500 millilitres, a 1.5 litre volume cell and 850 g, at £9.89. The Invigortex 3 litre bucket agrees at 3000 millilitres and 1.2 kg, at £10.99. McMillan agrees at 10 litres and 10000 millilitres, at £26.95, with no printed weight. The B2C 1 litre title does not: the volume cell says 360 litres and the unit count says 100 gram.
Review texts are the contamination check. On the shared Invigortex bag file they name plastic, rubber, glass shards, slug or snail eggs, peat, wood and live worms. On the bucket file they name plastic, a rock and eggs, beside shorter praise. On the B2C files, two texts mention a clear or unexpected bag, and the shared 1 litre and 100 litre texts include a short measure and an unbranded bag.
Three typical situations, each with a recommendation from this comparison.
You need a small pack whose litre cells agree, for a thin top-dress or a small share of a peat-free mix. B2C worm castings, 1.5 litres, is £9.89, granules from Poland, stated weight 850 g, rated 3.8 from 22. Two review texts mention a clear bag. No scheme is named.
You want the lower price per litre among packs whose cells agree, and you have read the feedstock line. McMillan worm humus is £26.95 for 10 litres, about £2.70 per litre, a powder from Italy. The line is 5.0 from 1, with no review text, and a bullet says larvae and chitin.
You want a UK-origin 3 litre title whose litre cells agree, and you will confirm the parcel. The Invigortex 3 litre bucket listing is £10.99, stated weight 1.2 kg, rated 4.0 from 17. Those review texts are shared, and buyers who name a size say a bag arrived.
The highest score in this folder is B2C worm castings, 1.5 litres, and only as the small granule bag whose litre cells agree. It is £9.89, about £6.59 per litre, rated 3.8 from 22, and clear-bag comments are the limit. It is not a UK-wide winner and it is not PAS 100 or Soil Association certified. The best value is McMillan worm humus, 10 litres, at £26.95, about £2.70 per litre, and only because those cells agree. One rating, no review text, no printed weight and a larva-and-chitin bullet mean it is a different product from earthworm castings. The cheaper-looking 40 litre and 100 litre titles are not the value pick, because their kilogram cells do not match the title.
McMillan worm humus, 10 litres
Best value only on price per agreed litre: £26.95 for 10 litres is about £2.70 per litre, with one rating and a larva bullet.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources for this comparison. amazon.co.uk listings were read on 16 October 2026.
This page contains affiliate links to amazon.co.uk. If you buy through them, we may earn a commission at no extra cost to you. Prices and ratings are from the 16 October 2026 listings. We did not run a laboratory soil test.
