The best sauna stones, compared.
Top pick: UPKOCH 3 spheres Best value: Toyvian 1 kg 2–3 cm – Lowest shelf price, about £11.19 for a stated 1 kg, useful only as a top-up where the manual allows 2–3 cm stones. Updated October 2026.
Sauna stones are the rocks in a heater. They store heat and make steam when you pour water on them. You are filling a new heater, replacing crumbled stones, or checking whether a cheap lava-rock bag is the same thing. It is not. Match the heater manual on material, diameter and kilograms, and cover the elements without packing them tight. That order is on the [sauna stones buying guide](/hub/steam-baths/sauna-stones/sub/sauna-stones-buying-guide). Harvia names peridotite, olivine diabase, olivine and, on some models, vulcanite, and says to keep ceramic stones and soft soapstone out of many electric heaters. Many electric heaters use about 5–10 cm. HUUM’s published fills run from about 40 kg to 250 kg. A 1 kg bag does not fill a normal heater. This page compares six amazon.co.uk listings read on 16 October 2026, from about £11.19 to about £141.18. Scores use stated type, size and mass, review evidence, whether the pack matches its implied job, and the shelf price. They are not a laboratory test.
Sauna stones are the rocks in a heater. They store heat and make steam when you pour water on them. You are filling a new heater, replacing crumbled stones, or checking whether a cheap lava-rock bag is the same thing.
22 products checked · 48 hrs invested · +16,800 readers
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Personal buying guide
Question 1 of 2
What are you trying to fill?
UPKOCH provides three round volcanic-stone spheres of about 5 cm, with a listed pack weight around 222 g. That diameter could resemble a heater stone, but three pieces are nowhere near a normal sauna charge. The 5.0 rating comes from only two reviews, and neither reviewer used the stones in a sauna: one used them for a school project and fireplace décor, while the other hung them in a car as a diffuser. One review also mentions grit, which matters when stones should be rinsed clean before heater use. Although the listing mentions electric and wood-burning heaters, its strong aroma-diffuser positioning makes the intended role unusually broad. Treat this as a tiny accessory or sample only after checking the manual, not as evidence-backed sauna-heater stones.
Pros
Cons
Best for: A three-stone decorative or aroma use, or a manual-approved replacement of exactly this size.
Less suitable: Filling or meaningfully topping up any normal sauna heater.
Specifications
Common questions
Do the stones come with a scent?
No. A page question asks if any scents are included. The bullets tell you to add essential oil. One UK review hung them in a car and found the scent subtle. Oil on heater stones is a separate risk: use only what the heater maker allows.
What did the two UK reviews actually use them for?
One review used them for a school rock project and then as fireplace décor, and mentioned grit. The other hung them in a car. Neither describes a sauna heater.
Does the listing name a wood stove?
Yes. A bullet says the stones work from an electric heater to a wood stove, and also as a car diffuser. The pack is three spheres at about 222 g, which is not a stove fill.
Saunom supplies roughly 15–16 kg of vulcanite and names both electric and wood-burning sauna heaters, giving it the clearest full-charge positioning in this comparison. Its 4.6 rating from 36 reviews supports the top-pick score, but the extracted review text is from the United States rather than verified UK use. Several reviewers praise the size mix and the steam produced when water is added. Against that, one mentions grit after rinsing and another says stones blew up, so the listing does not justify a no-crack claim. The product page also conflicts with itself, giving a 2–3.5 inch range in one place and a 2.54 cm cube in the technical table. At £141.18, buy only after the seller confirms the size range and your heater manual accepts vulcanite.
Pros
Cons
Best for: A 15 kg-class fill for an electric or wood-burning heater that explicitly accepts vulcanite and the confirmed size range.
Less suitable: Buyers needing verified UK review evidence, a low price or a tightly specified stone diameter.
Specifications
Common questions
Does the listing say the stones suit an electric heater?
Yes. The title names electric and wood-burning sauna heaters. A page question asks the same thing. One US review mentions a 2 kW heater. The pack is stones only.
What size does the page actually give?
A bullet says 2 to 3.5 inches and a mix of sizes. The technical table says 2.54 x 2.54 x 2.54 cm at 16.06 kg. Those two size lines are not reconciled. Confirm the range with the seller.
Where were the extracted reviews written?
The extract marks them reviewed in the United States. The average on the listing is 4.6 from 36 ratings. Themes include steam when water is added, leftover stones, grit after rinsing, and one report of rocks blowing up.
Willowybe’s box provides about 16 kg, making it one of only two products here that could approach a complete charge for a smaller heater. Its 3.9 rating is based on 247 reviews, a much broader evidence base than the other kept listings. The experience is mixed: some reviewers report useful steam and no cracks, while others describe popping or stones breaking during early heats. A UK review says roughly half the box was too large to fit and too difficult to break, despite the product table giving dimensions around 2.5 cm. That conflict makes the heater manual and the actual gap between elements more important than the headline mass. At £128.30, it is a costly gamble unless the supplier can confirm the size range for your model.
Pros
Cons
Best for: A heater needing roughly 16 kg where the supplier confirms the delivered stone-size range.
Less suitable: Tight electric elements, buyers planning to break oversized stones, or anyone wanting consistent review reports.
Specifications
Common questions
Does the box include a sauna heater?
No. A question on the page asks, and the bullets describe stones only. You still need a heater that the manual says can take this mass and size.
What do reviewers say about the size?
A UK review on 26 September 2025 says only half the stones were usable and the rest were too big to break with a hammer. Other reviews say the size filled their stove. The table’s 2.5 cm line does not match those large-stone comments.
Do the reviews mention cracking?
Yes. Several reviews describe popping or exploding on the first heats. Others report no cracks after rinsing and a few sessions. The listing average is 3.9 from 247 ratings.
The Toyvian bag provides 1 kg of small, 2–3 cm stones for £11.19, so it makes more sense as a measured top-up than as a complete heater charge. Its low shelf price is useful when your manual calls for this diameter and you only need to replace a few damaged stones. The listing describes volcanic or lava rock and mentions heater use, but it does not name a compatible heater model. There is no customer-review line on the listing, leaving no independent evidence about cracking, dust or durability. The catalogue also labels the stones as “ac”, which is not meaningful compatibility information for a passive bag of rocks. Check both the diameter and required kilograms in your heater manual before you treat the low price as a full recommendation.
Pros
Cons
Best for: A low-cost top-up where the heater manual specifically permits 2–3 cm volcanic stones.
Less suitable: Filling a heater that needs larger stones or substantially more than 1 kg.
Specifications
Common questions
Does the listing say these are for a home sauna?
A question on the page asks if they can be used in a home sauna. The bullets call them indoor sauna stones and also outdoor sauna stones. No heater model is named.
How much stone is in the bag?
The table lists 1 kg and dimensions of 3 x 2.5 x 2 cm. The title says 2–3 cm. A piece count is not on the listing. Treat it as a 1 kg top-up, not a heater fill.
Is there a star rating?
The listing has no customer-reviews line, so the rating and the review count are not available. Do not read the low price as review evidence.
The Lurrose pack contains ten 2–3 cm basalt stones and explicitly names an electric sauna, but its quantities are difficult to reconcile. The technical table gives a total weight of only 151 g, which would make this a very small replacement set rather than a heater fill. Its £18.19 price therefore needs to be judged against ten individual stones, not against the 15–20 kg boxes commonly used for small heaters. The listing says the basalt has no artificial coating, yet there are no customer reviews on the listing to support claims about noise or durability. Its “ac” power-source field is merely a catalogue entry and does not show compatibility with a 230 V UK heater. This pack is defensible only when your manual permits 2–3 cm stones and you have counted exactly how few replacements you need.
Pros
Cons
Best for: Replacing a small number of 2–3 cm stones in a heater whose manual permits that size.
Less suitable: A first fill, a large top-up, or buyers who need a reliable kilogram figure.
Specifications
Common questions
What does the listing say they are made of?
The title says volcanic basalt. A bullet says natural volcanic sauna rocks without artificial coatings or added chemicals. That is the listing’s wording, not a lab result.
Does the page mention crackling?
A question on the page asks if they crackle when heated. A bullet says the design helps release warmth with less popping noise. There are no reviews on the listing to check that claim.
Why are the weight figures hard to read together?
The table lists 151 g. The title is a 10-pack of 2.00–3.00 cm stones. Both figures are on the listing and are not reconciled. Do not treat 151 g as a heater fill.
Veemoon supplies about 1.04 kg of 2–3 cm stones, which is a top-up quantity rather than a normal full charge. At £19.63, it costs considerably more than the similar 1 kg Toyvian bag in this comparison. More importantly, the title presents the same stones for both a sauna heater and a fire pit, even though those applications are not interchangeable by default. The listing names no heater model or manual specification that resolves that ambiguity. There is also no customer-review line on the listing, so there is no practical evidence here about dust, fit or cracking. Buy only if your heater manufacturer accepts this exact stone type and small diameter; the broad product wording is not enough on its own.
Pros
Cons
Best for: A small replacement quantity after the heater manual confirms both the material and 2–3 cm size.
Less suitable: A complete heater fill, or anyone relying on the fire-pit wording as proof of sauna suitability.
Specifications
Common questions
Does the listing mention a fire pit?
Yes. The title says lava stones for a fire pit, and a page question asks if they can be used in a fire pit. The same bullets also say sauna heater rocks. Those uses are not the same by default.
How heavy is the pack?
The technical table says 1.04 kg and 3 x 2.5 x 2 cm. The title says 1 kg and 2–3 cm. Either figure is a top-up, not a normal heater charge.
Is there a star rating?
The listing has no customer-reviews line, so the rating and the review count are not available. The fire-pit wording is not a substitute for reviews.
Scores are editorial comparison scores from the amazon.co.uk listings read on 16 October 2026. They are not laboratory results and not a direct conversion of Amazon stars. Points come from heater suitability and how clearly the listing states stone type, diameter and pack mass, from relevant customer reviews, from whether the quantity fits the stated role, from value at the listed GBP price, and from listing consistency. Deductions cover conflicting dimensions, reviews about a different use, a pack that is too small for its apparent role, vague heater compatibility, and reports of poor fit, grit, popping or cracking. A product with no customer-review line can still score for clear specifications and value, and it cannot receive full evidence points.
Heater fit and stated spec
35%Material, diameter and pack mass need to be clear, and they need to match a heater role. A named electric or wood-burning heater scores above a title that also sells the same bag as a fire pit.
Relevant reviews
25%Stars and review volume count when the comments are about heater stones. A school project, fireplace décor or a car diffuser is not evidence of a sauna session.
Quantity for the role
20%A 15 kg-class box can approach a small heater fill. A 1 kg bag or three spheres is a top-up or a sample, and it is scored as that.
Shelf price
15%Value is the listed GBP price against the mass and the clarity of the listing. A low price does not turn a 1 kg bag into a full charge.
Listing consistency
5%Conflicting size or weight lines, and a catalogue field such as “ac” on a bag of rocks, reduce confidence. The score is an aid, not a test certificate.
Match the heater manual on material, diameter and kilograms before you compare the shelf price. A 1 kg bag and a 15 kg box are different jobs. Fire-pit lava is a third product.
Sauna stones store heat in the heater and turn a small ladle of water into steam. Buy them against the heater manual, not against a product title. The manual sets the material, the diameter and the kilograms. Many electric heaters take stones around 5–10 cm. Some wood burners take 10–15 cm. HUUM lists 3–5 cm for CLIFF. Olivine diabase is Harvia’s default for all heater types. Peridotite and olivine are the other natural types in that FAQ. Vulcanite appears on some models.
Toyvian is 1 kg, Veemoon is 1.04 kg, Lurrose lists 151 g and UPKOCH is about 222 g. A small wall heater may still need a 20 kg box. HUUM’s published fills run from about 40 kg to 250 kg.
Garden lava, quartz, river rock and stones from a stream are not heater stones because they look volcanic. Veemoon’s fire-pit wording does not prove sauna use. Match the type the manual allows.
Stones should support each other, cover the elements and leave air gaps. Do not rest their weight on the elements. Pour about 0.2 litres on the stones, not a jug onto hot steel, and not oil unless the pack is a sauna aroma the heater maker allows.
The heater manual is the first filter. It names the materials, the diameter and the kilograms. Many electric heaters are about 5–10 cm. Some wood burners use 10–15 cm. HUUM lists 3–5 cm for CLIFF. Olivine diabase is Harvia’s default for all heater types. Peridotite and olivine are the other natural types that FAQ allows. Vulcanite is a dark trade stone used on some models. It is not a no-crack promise.
A pack is either close to a charge or it is a top-up. HUUM publishes about 40 kg (CORE), 55 kg (DROP), 75 kg (CLIFF) and 250 kg (HIVE). A small wall heater may be one 20 kg box plus a few spares. Saunom’s table is 16.06 kg and the title says 33 lb. Willowybe’s table is 15.85 kg and the title is about 16 kg. Those two can approach a smaller fill if the size is confirmed. Toyvian at 1 kg and Veemoon at 1.04 kg cannot. Lurrose’s 151 g and UPKOCH’s 222 g are smaller still.
Three typical situations, each with a recommendation from this comparison.
You need a pack that can approach a full charge, not a 1 kg top-up. Saunom names electric heaters and lists 16.06 kg on the table, at about £141.18. The bullet and the table disagree on size, and the extracted reviews are from the United States. Confirm vulcanite and the size range in the heater manual before you order.
If the manual allows 2–3 cm volcanic stones and you only need to replace damaged pieces, the Toyvian 1 kg bag is about £11.19. It has no customer-review line. It will not fill a heater that needs 15–20 kg. A crumbled full charge is usually one or two 15–20 kg boxes of the diameter the manual already specifies.
A wood-burning heater still follows its own manual. Saunom names wood-burning heaters as well as electric ones, with the same size conflict. Veemoon puts a fire pit and a sauna heater in one title. Fire-pit lava, river rock and stones from a stream are not a substitute for the type the manual allows.
The top pick is Willowybe 16 kg box, with the highest score in this comparison (6.9 out of 10, from 247 amazon.co.uk reviews). The best value is the Toyvian 1 kg bag at about £11.19. That price is for a measured top-up of 2–3 cm stones, not for filling a heater. There is no customer-review line on that listing.
Toyvian 1 kg 2–3 cm
Lowest shelf price, about £11.19 for a stated 1 kg, useful only as a top-up where the manual allows 2–3 cm stones.
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.
Heater-maker guidance, UK product-safety pages and one UK shop price. Listings checked 16 October 2026. Prices on amazon.co.uk move.
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. Scores compare published listings and review texts. They are not a laboratory test.
