See it at HUUM: HIVE Wood 13
HUUM's own page for the HIVE Wood 13. Not a paid link.
Sauna heater size calculator
Heater makers size for about 1 kW per cubic metre of room, roughly 1 kW per 35 cubic feet, and more when the room has glass, bare stone or uninsulated log walls. Enter your room to see the output that calls for, the heaters rated for it and the pre-fab kits that fit your space.
Work out your heater size
Enter the inside of your hot room. The calculator gives its volume, the volume Harvia's and HUUM's rules say to size for, and the heaters in our catalogue whose makers rate them for it. Below that, enter the space you have for a pre-fab kit.
1. Your hot room
Room volume: 294 ft³ (8.3 m³)
Harvia's rule: size for 345 ft³ (9.8 m³), about 9.8 kW.
HUUM's rule: size for 337 ft³ (9.5 m³), about 9.5 kW.
Heaters rated for that room (16)
- HUUM HIVE Wood 13 · HUUM · 13 kW · rated for 6–13 m³ (about 212–459 ft³, our conversion)Your room sits in the middle of its rated range. Matched by HUUM's own rule.
- Harvia Legend 150 wood-burning heater · Harvia · 16 kW · rated for 6–13 m³ (about 212–459 ft³, our conversion)Your room sits in the middle of its rated range. Matched by Harvia's own rule.
- Harvia M3 wood-burning heater · Harvia · 16.5 kW · rated for 212–459 ft³ (about 6–13 m³, our conversion)Your room sits in the middle of its rated range. Matched by Harvia's own rule.
- Harvia KIP80B 8 kW 240VAC · Harvia · 8 kW · rated for 251–424 ft³ (about 7.1–12 m³, our conversion)Your room sits in the middle of its rated range. Matched by Harvia's own rule.
- HUUM DROP 7 · HUUM · 7.5 kW · rated for 7–11 m³ (about 247–388 ft³, our conversion)Your room sits in the middle of its rated range. Matched by HUUM's own rule.
- HUUM CLIFF 9 · HUUM · 9 kW · rated for 8–13 m³ (about 283–459 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by HUUM's own rule.
- HUUM CORE 9 · HUUM · 9 kW · rated for 8–13 m³ (about 283–459 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by HUUM's own rule.
- HUUM DROP 9 · HUUM · 9 kW · rated for 8–13 m³ (about 283–459 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by HUUM's own rule.
- HUUM HIVE Mini 9 · HUUM · 9 kW · rated for 8–13 m³ (about 283–459 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by HUUM's own rule.
- HUUM STEEL 9 · HUUM · 9 kW · rated for 8–13 m³ (about 283–459 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by HUUM's own rule.
- Saunum Air L 10 · Saunum · 10 kW · rated for 283–494 ft³ (about 8–14 m³, our conversion)Your room is inside its rated range, toward one end. Matched by Harvia's rule; Saunum may size differently, so check its manual.
- HUUM HIVE Flow · HUUM · 9.8 kW · rated for 8–18 m³ (about 283–636 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by HUUM's own rule.
- Narvi Stony 20 · Narvi · rated for 8–20 m³ (about 283–706 ft³, our conversion)Your room is inside its rated range, toward one end. Matched by Harvia's rule; Narvi may size differently, so check its manual.
- Harvia Pro 20 ES wood-burning heater · Harvia · 24.1 kW · rated for 283–706 ft³ (about 8–20 m³, our conversion)Your room is inside its rated range, toward one end. Matched by Harvia's own rule.
- Kuuma Low Profile (Small) · Kuuma · rated for 336–448 ft³ (about 9.5–12.7 m³, our conversion)Your room is inside its rated range, toward one end. Matched by Harvia's rule; Kuuma may size differently, so check its manual.
- Kuuma Classic Legacy (Small) · Kuuma · rated for 336–512 ft³ (about 9.5–14.5 m³, our conversion)Your room is inside its rated range, toward one end. Matched by Harvia's rule; Kuuma may size differently, so check its manual.
2. A pre-fab kit that fits your space
Kits whose outside dimensions fit (5)
- Almost Heaven Saunas Worthington 4-6 Person Indoor Sauna · Almost Heaven Saunas · Indoor sauna · seats 4–6Outside, as Almost Heaven Saunas lists it: 81⅞″W x 64³⁄₁₆″D x 80⁵⁄₁₆″H (81.9″ × 64.2″ floor, 80.3″ tall). Heater: Best-in-class heater & sauna stones.
- Almost Heaven Saunas Titan 6 Person Indoor Sauna · Almost Heaven Saunas · Indoor sauna · seats 6Outside, as Almost Heaven Saunas lists it: 83 ¼″W x 72 ¼″D x 79 ⅜″H (83.3″ × 72.3″ floor, 79.4″ tall). Heater: Options include: 8kW KIP Heater w/ Dials; 8kW Spirit Smart Heater + Fenix; 9kW Virta Smart Heater + Fenix.
- Almost Heaven Saunas Patterson 6 Person Indoor Sauna · Almost Heaven Saunas · Indoor sauna · seats 6Outside, as Almost Heaven Saunas lists it: 81⅞″W x 81⅞″D x 80⁵⁄₁₆″H (81.9″ × 81.9″ floor, 80.3″ tall). Heater: Best-in-class heater & sauna stones.
- Finnleo Centurion (Designer Series) · Finnleo · Indoor sauna · seats 4–5Outside, as Finnleo lists it: 84" W x 72" D x 84" H (84″ × 72″ floor, 84″ tall). Heater: Himalaya 7.0 kW.
- Almost Heaven Saunas Rainelle 4 Person Indoor Sauna · Almost Heaven Saunas · Indoor sauna · seats 4Outside, as Almost Heaven Saunas lists it: 71½″W x 62¾″D x 77⅝″H (71.5″ × 62.8″ floor, 77.6″ tall). Heater: Options include: 6kW KIP Heater w/ Dials; 6kW Spirit Smart Heater + Fenix; 8kW Virta Smart Heater + Fenix.
10 more kits fit that space and headcount, but their makers do not say whether they are for indoor or outdoor use. Check before you plan on one: Almost Heaven Saunas Lewisburg 6-8 Person Barrel Sauna, Almost Heaven Saunas Seneca 6 Person Barrel Sauna, Almost Heaven Saunas Princeton 6 Person Barrel Sauna, Almost Heaven Saunas Evander Half-Moon Canopy Barrel Sauna, Almost Heaven Saunas Magnus 6 Person Canopy Barrel Sauna, Almost Heaven Saunas Watoga 2-4 Person Barrel Sauna, Almost Heaven Saunas Audra 2-4 Person Canopy Barrel Sauna, Almost Heaven Saunas Pinnacle 4 Person Barrel Sauna, Almost Heaven Saunas Essex 4 Person Barrel Sauna, Almost Heaven Saunas Charleston 4 Person Canopy Barrel Sauna.
1 more kit suits your headcount and placement but publishes no outside dimensions we could read: Scandia DIY PreCut Sauna Kit.
A planning tool, not a guarantee
This calculator is a planning aid, nothing more. It applies the sizing rules heater makers publish to the numbers you enter, and it lists products by the figures their makers publish. It makes no guarantee that a heater will heat your room as you want, that a kit will fit your space or pass inspection, or that any figure is current. Makers revise their products and ratings. Before you buy or build, follow the heater's and the kit's installation manuals, including clearances and ventilation, check your local building code and permit rules, and have a licensed electrician confirm the circuit, breaker and wiring. Saunakivi has not tested these products.
How it works: about 1 kW of heater output per cubic metre of room. Harvia counts each square metre of glass, stone or other uninsulated surface as 1.2 cubic metres and applies a factor of 1.5 for uninsulated log walls; HUUM adds the area of such surfaces to the volume; for log walls we count the four walls' area, less any glass, which is our reading of HUUM's rule. Harvia and HUUM heaters are matched by their own maker's rule, every other heater by Harvia's, and a heater is listed when its maker's rated room range covers the result. Kits are matched on the outside dimensions their makers publish, plus the space you ask to leave around them.
Where to buy the heaters the example lists
HUUM HIVE Wood 13
As an Amazon Associate we earn from qualifying purchases. Some links on this page are paid: if you buy after following one, the retailer pays Saunakivi (IPORA LLC) a commission. It costs you nothing extra, and it never changes the specifications we list.
- Select Saunas
Amazon
Sold via a marketplace listing — the seller may not be the brand or an authorized retailer.
Harvia Legend 150 wood-burning heater
Paid links · how this works
- Select Saunas
Amazon
Sold via a marketplace listing — the seller may not be the brand or an authorized retailer.
See it at Harvia: Legend 150 wood-burning heater
Harvia's own page for the Legend 150 wood-burning heater. Not a paid link.
Harvia M3 wood-burning heater
Paid links · how this works
- Select Saunas
Amazon
Sold via a marketplace listing — the seller may not be the brand or an authorized retailer.
See it at Harvia: M3 wood-burning heater
Harvia's own page for the M3 wood-burning heater. Not a paid link.
Harvia KIP80B 8 kW 240VAC
Paid links · how this works
- Select Saunas
Amazon
Sold via a marketplace listing — the seller may not be the brand or an authorized retailer.
See it at Harvia: KIP80B 8 kW 240VAC
Harvia's own page for the KIP80B 8 kW 240VAC. Not a paid link.
HUUM DROP 7
Paid links · how this works
- Select Saunas
Amazon — with UKU Local control (Black)
Sold via a marketplace listing — the seller may not be the brand or an authorized retailer.
See it at HUUM: DROP 7
HUUM's own page for the DROP 7. Not a paid link.
HUUM CLIFF 9
Paid links · how this works
- Select Saunas
Amazon — with UKU WiFi control (Black)
Sold via a marketplace listing — the seller may not be the brand or an authorized retailer.
See it at HUUM: CLIFF 9
HUUM's own page for the CLIFF 9. Not a paid link.
These are the first 6 heaters the calculator lists for its opening example, a 7 by 6 ft room, 7 ft tall with a 13 sq ft glass door. Your room will differ: enter it above, and check the heater's installation manual and your electrician before you buy.
The rules it applies
- Harvia: about 1 kW of heater power for every cubic metre of room volume; each square metre of glass, stone or other uninsulated surface counts as 1.2 cubic metres; a factor of 1.5 for uninsulated log walls; and a heater whose rated range puts your room near its middle.
- HUUM: one kilowatt per calculated cubic metre, after adding the area of uninsulated surfaces, such as a glass door, a glass wall or an uninsulated log wall, to the room volume. For log walls the calculator counts the four walls' area, less any glass: that is our reading of HUUM's rule, not a figure HUUM gives.
Room sizes are shown in the maker's own unit with the other unit after it; figures marked "about" are our conversions. The heater sizing guide sets out each rule with its source.
Questions
How many kW sauna heater do I need?
About 1 kW for every cubic metre of room, by Harvia's and HUUM's published rules, before any allowance for glass or masonry. A 7 by 6 ft room, 7 ft tall is 294 cubic feet, or 8.3 cubic metres, so about 8.3 kW.
Sources: How do I select the correct heater power?; Sauna Heater Size Calculator: How to Choose the Right Power Rating for Your Sauna?
Does a glass door change the heater size?
Yes, by both makers' rules. Harvia counts each square metre of glass as 1.2 cubic metres of extra room: add a 13 sq ft glass door to the 7 by 6 ft room, 7 ft tall and Harvia's figure rises from about 8.3 to about 9.8 cubic metres, so about 9.8 kW. HUUM's rises to about 9.5.
Sources: How do I select the correct heater power?; Sauna Heater Size Calculator: How to Choose the Right Power Rating for Your Sauna?
Will a pre-fab sauna kit fit my space?
Compare the kit's outside dimensions, as its maker lists them, with your floor space and, indoors, your ceiling height, and leave the clearances the kit's installation manual gives. The calculator does that comparison for the kits in our catalogue whose makers publish outside dimensions.