Free calculator
Sauna Heater Size Calculator
Enter your sauna's inside size, its glass and wall type. Get the heater kW it needs, the 240 V breaker and wire gauge, whether you need a contactor, the cost per session at your state's rate, and heaters rated for your room. Planning an infrared cabin instead? Pick infrared at step 1.
Updated Oct 24, 2026
- Answer a few questions
- See the math behind every number
- Get models that actually fit
Every sauna heater this tool can recommend
Sorted by kW. Room ranges, amps and what is in the box come from each listing or the maker's spec.
VEVOR 2kW 120V Sauna Heater
- 120V
- 53 to 88 cu ft
- Dial controls
- 3 h timer
+1 moreFewer
- Stones not included
A 2 kW, 120 V wall-mounted heater with dial controls for very small saunas of 53 to 88 cu ft. Stones are sold separately.
- Runs on 120 V, no 240 V circuit
- Dial thermostat to 230 F and 3-hour timer
- 304 stainless steel heating element
- Rated for 88 cu ft at most
- Needs 22 to 33 lb of stones, not included
- No UL or ETL listing stated on the listing
$100 to $250, live price on Amazon
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VEVOR 4.5kW 240V Sauna Heater
- 240V
- 105 to 210 cu ft
- Dial controls
- 3 h timer
+1 moreFewer
- Stones not included
A 4.5 kW, 240 V wall-mounted heater with dial controls for 105 to 210 cu ft rooms. Stones are sold separately.
- 304 stainless steel body and element
- Dial thermostat to 230 F and 3-hour timer
- Pre-drilled wall bracket
- Needs 22 to 33 lb of stones, not included
- No UL or ETL listing stated on the listing
$100 to $250, live price on Amazon
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Mxmoonant 4.5kW Sauna Heater
- 240V
- 100 to 210 cu ft
- Built-in knobs
- Stones not included
A 4.5 kW wall-mounted heater with built-in time and temperature knobs for 100 to 210 cu ft rooms. Stones are sold separately.
- Built-in time and temperature control
- Stainless steel heating elements
- Wall-mounted
- Needs 30 to 40 lb of stones, not included
- No plug: hardwired by an electrician
$250 to $500, live price on Amazon
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Finlandia FLB-45 4.5kW Sauna Heater
- 240V
- 100 to 210 cu ft
- UL listed
- 8 h preset timer
+1 moreFewer
- 24 x 16 x 11 in
A UL-listed 4.5 kW Finlandia wall heater with built-in thermostat, 60-minute timer and 1 to 8 hour preset, for 100 to 210 cu ft rooms.
- UL listed per the listing
- 1 to 8 hour preset timer to start heating ahead
- Large rock capacity, rocks touch the elements
- Stones not stated as included
$1,000 to $2,000, live price on Amazon
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Show all 22 modelsShow fewer
Harvia KIP 4.5kW Sauna Heater
- 240V
- 106 to 212 cu ft
- 18.8 A
- Stones included
+1 moreFewer
- Built-in controls
Harvia's 4.5 kW stainless KIP with built-in controls and stones in the box, for 106 to 212 cu ft rooms, drawing 18.8 A at 240 V.
- Sauna stones included
- Built-in controls on the heater
- Stainless steel, made by Harvia
- Controls are on the heater, inside the hot room
$1,000 to $2,000, live price on Amazon
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VEVOR 6kW 240V Sauna Heater
- 240V
- 177 to 318 cu ft
- Dial controls
- 3 h timer
+1 moreFewer
- Stones not included
A 6 kW, 240 V wall-mounted heater with dial controls for 177 to 318 cu ft rooms. Stones are sold separately.
- 304 stainless steel body and element
- Dial thermostat to 230 F and 3-hour timer
- Pre-drilled wall bracket
- Needs 22 to 33 lb of stones, not included
- No UL or ETL listing stated on the listing
$100 to $250, live price on Amazon
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Mxmoonant 6kW Digital Sauna Heater
- 240V
- 170 to 300 cu ft
- Digital display
- 180 min timer
+1 moreFewer
- Stones not included
A 6 kW wall-mounted heater with a built-in digital display, 0 to 180 minute timer and 86 to 230 F range, for 170 to 300 cu ft rooms. Stones are sold separately.
- Built-in digital display with live temperature
- 0 to 180 minute timer, 86 to 230 F
- Sauna hygrothermograph in the box
- Needs 30 to 40 lb of stones, not included
- No plug: hardwired by an electrician
$250 to $500, live price on Amazon
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Finlandia FLB-60 6kW Sauna Heater
- 240V
- 170 to 300 cu ft
- UL listed
- 8 h preset timer
+1 moreFewer
- 24 x 16 x 11 in
A UL and ETL listed 6 kW Finlandia wall heater with built-in thermostat, 60-minute timer and 1 to 8 hour preset, for 170 to 300 cu ft rooms.
- UL and ETL listed per the listing
- 1 to 8 hour preset timer to start heating ahead
- Large rock capacity, rocks touch the elements
- Stones not stated as included
$1,000 to $2,000, live price on Amazon
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Harvia KIP 6kW Sauna Heater
- 240V
- 170 to 300 cu ft
- 25 A
- Stones included
+1 moreFewer
- Dial controls
Harvia's 6 kW dual-wall stainless KIP with built-in dial controls, stone guard and a box of olivine diabase stones, for 170 to 300 cu ft rooms.
- Olivine diabase stones and stone guard included
- Dual-wall body stays cooler to the touch
- Built-in dial controls
- Controls are on the heater, inside the hot room
$1,000 to $2,000, live price on Amazon
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Amerec Designer DSNR-60B 6kW Sauna Heater
- 240V
- 175 to 310 cu ft
- Rocks included
- Built-in controls
Amerec's 6 kW Designer heater with built-in controls and Vulcanite rocks, for 175 to 310 cu ft rooms on Amerec's chart.
- Vulcanite rocks included
- Built-in control, no separate panel
- 240 V single phase
- Controls are on the heater, inside the hot room
$1,000 to $2,000, live price on Amazon
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Harvia KIP60W with Xenio Wi-Fi Control
- 240V
- Wi-Fi
- 170 to 300 cu ft
- Xenio Wi-Fi control
+2 moreFewer
- UL listed
- Stones included
Harvia's 6 kW KIP-W heater packaged with the Xenio CX170 touch control with Wi-Fi and stones, UL listed, for 170 to 300 cu ft rooms.
- Xenio CX170 touch control with Wi-Fi in the box
- UL listed per the listing
- Stones included
- Costs well over the same-size KIP with dial controls
Over $2,000, live price on Amazon
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Amerec 6kW Sauna Heater with SaunaLogic2 and Contactor
- 240V
- Wi-Fi
- 175 to 310 cu ft
- SaunaLogic2 Wi-Fi
+2 moreFewer
- Contactor box
- Rocks included
A 6 kW Amerec heater package with the SaunaLogic2 Wi-Fi control panel, the contactor box and rocks, for 175 to 310 cu ft rooms.
- SaunaLogic2 Wi-Fi control and contactor box in the box
- Rocks included
- Auto shut-off and temperature sensors
- Control panel and contactor box mean more wiring than a built-in unit
Over $2,000, live price on Amazon
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HUUM DROP 6kW with UKU Control
- 240V
- 30 A of breakers
- 177 to 353 cu ft
- UKU wall control
+2 moreFewer
- 30 A breaker
- Stones included
HUUM's water-drop shaped 6 kW heater with exposed stones and the UKU wall control, door sensor and stones, for 177 to 353 cu ft rooms.
- UKU wall control panel, temperature and door sensors included
- HUUM lists a 30 A breaker and 10 AWG wire
- Stones included, 5-year limited warranty (not elements)
- UKU Local has no Wi-Fi; the Wi-Fi version costs more
Over $2,000, live price on Amazon
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Harvia Cilindro 6.8kW Sauna Heater
- 240V
- 140 to 334 cu ft
- 200 lb stones included
- Floor-standing
+1 moreFewer
- Built-in controls
A floor-standing 6.8 kW Harvia Cilindro tower with built-in controls and 200 lb of Harvia stones, for 140 to 334 cu ft rooms.
- 200 lb of stones included
- Built-in controls
- Wide 140 to 334 cu ft range
- Floor-standing, needs floor space and clearance
- Draws 28.8 A per the listing
$1,000 to $2,000, live price on Amazon
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Harvia KIP80B 8kW Sauna Heater
- 240V
- 250 to 425 cu ft
- 33.3 A
- Stones included
+1 moreFewer
- Built-in controls
Harvia's 8 kW KIP with built-in controls and stones included, for 250 to 425 cu ft rooms, 16.1 x 11 x 23.6 in.
- Sauna stones included
- Cool-touch dual-wall stainless body
- Made in Finland, 1-year limited warranty
- Draws 33.3 A, so a 45 A circuit
- Controls are on the heater, inside the hot room
$1,000 to $2,000, live price on Amazon
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Amerec Designer DSNR-80B 8kW Sauna Heater
- 240V
- 240 to 425 cu ft
- Rocks included
- Built-in controls
Amerec's 8 kW Designer heater with built-in controls and Vulcanite rocks, for 240 to 425 cu ft rooms on Amerec's chart.
- Vulcanite rocks included
- Built-in control, no separate panel
- 240 V single phase
- Controls are on the heater, inside the hot room
$1,000 to $2,000, live price on Amazon
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Amerec 8kW Sauna Heater with SaunaLogic2 and Contactor
- 240V
- Wi-Fi
- 240 to 425 cu ft
- SaunaLogic2 Wi-Fi
+2 moreFewer
- Contactor box
- Rocks included
An 8 kW Amerec heater package with the SaunaLogic2 Wi-Fi control panel, the contactor box and rocks, for 240 to 425 cu ft rooms.
- SaunaLogic2 Wi-Fi control and contactor box in the box
- Rocks included
- Auto shut-off and temperature sensors
- Control panel and contactor box mean more wiring than a built-in unit
Over $2,000, live price on Amazon
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VEVOR 9kW 240V Sauna Heater with External Controller
- 240V
- 318 to 459 cu ft
- External digital control
- Preset start
+1 moreFewer
- Stones not included
A 9 kW, 240 V wall-mounted heater with an external digital controller and preset start, for 318 to 459 cu ft rooms. Stones are sold separately.
- External digital controller included
- Preset mode for auto start and stop
- Up to 4 hours heating per session
- Needs 22 to 33 lb of stones, not included
- No UL or ETL listing stated on the listing
$250 to $500, live price on Amazon
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Mxmoonant 9kW Digital Sauna Heater (ETL)
- 240V
- 265 to 460 cu ft
- ETL listed
- Digital display
+1 moreFewer
- Stones not included
An ETL-listed 9 kW wall-mounted heater with a built-in digital display for 265 to 460 cu ft rooms. Stones are sold separately.
- ETL certified per the listing
- Built-in digital time and temperature control
- Wall-mounted
- Needs 30 to 40 lb of stones, not included
- No plug: hardwired by an electrician
$500 to $1,000, live price on Amazon
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Harvia Cilindro 9kW Sauna Heater with Stones
- 240V
- 280 to 490 cu ft
- 37.5 A
- Stones included
+1 moreFewer
- Floor-standing
A floor-standing 9 kW Harvia Cilindro with built-in control and five boxes of stones, for 280 to 490 cu ft rooms, 37.5 A at 240 V.
- Five boxes of sauna stones included
- Built-in control
- 280 to 490 cu ft range
- Floor-standing, needs floor space and clearance
- Draws 37.5 A, so a 50 A circuit
$1,000 to $2,000, live price on Amazon
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Harvia Cilindro 9kW with Xenio Control and Power Unit
- 240V
- 280 to 490 cu ft
- Xenio control
- Power unit
+1 moreFewer
- Stones included
The floor-standing 9 kW Harvia Cilindro packaged with the Xenio control, its power unit and five boxes of stones, for 280 to 490 cu ft rooms.
- Xenio control and power unit included
- Five boxes of sauna stones included
- Set the sauna from a panel, not the heater
- Floor-standing, needs floor space and clearance
- Draws 37.5 A, so a 50 A circuit
Over $2,000, live price on Amazon
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HUUM DROP 9kW with UKU Control
- 240V
- 50 A of breakers
- 282 to 530 cu ft
- UKU wall control
+2 moreFewer
- 50 A breaker
- Stones included
HUUM's 9 kW DROP heater with the UKU wall control, door sensor and stones, for 282 to 530 cu ft rooms.
- UKU wall control panel, temperature and door sensors included
- Widest range here, up to 530 cu ft
- Stones included, 5-year limited warranty (not elements)
- HUUM lists a 50 A breaker and 8 AWG wire
- UKU Local has no Wi-Fi
Over $2,000, live price on Amazon
Check price on AmazonPaid link. We earn a commission at no cost to you.
Some of these links pay us a commission and some do not; each card says which. Commissions do not affect which models the tool picks or how it ranks them. See our disclosure.
How this calculator works
- Volume. Inside length x width x height in cubic feet.
- Adjustments. Harvia's heater manuals add 1.2 m³ of volume for every m² of uninsulated surface (glass, brick, concrete, stone, tile), which is about 4 cu ft per sq ft, and multiply the volume by 1.5 for solid log walls, which take longer to heat.
- kW. About 1 kW per 45 to 50 cu ft of the adjusted volume, the ratio behind the room ranges Harvia, Amerec and HUUM print (for example 8 kW for about 250 to 425 cu ft). We then match each heater on its own maker range, minimum to maximum, never on the rule alone.
- Circuit. Amps = kW x 1,000 / volts, or the maker's listed amps. A sauna heater is fixed electric space heating, so NEC 424.3(B) sizes the circuit at 125% of that, rounded up to the next standard breaker. Wire is copper: the NEC 310.16 75 C column for THHN, the 60 C column for NM-B cable, with the 240.4(D) small-conductor limits (10 AWG on 30 A at most). Where a maker publishes its own breaker size we show it, and its manual governs the install.
- Cost. Our assumption, not a maker figure: 40 minutes at full power to heat up (makers quote 30 to 60 minutes for a correctly sized, insulated room), then the thermostat cycles the elements about half the time while you sit. kWh x your state's average residential rate (EIA). Infrared cabins: 15 minutes preheat plus the session at the listed watts, or at the circuit's limit where the maker lists none.
Worked examples
6 x 5 ft indoor sauna with a full glass door
- 6 x 5 x 7 ft inside, 210 cu ft
- Full glass door, about 12 sq ft
- 45 minute sessions, 3 a week, US average 17.3 cents
Size for 258 cu ft: a 6 kW heater on a 35 A, 240 V circuit, about $1.08 a session.
The glass adds 12 x 4 = 48 cu ft, so size for 258 cu ft, or 5.2 to 5.7 kW by the 1 kW per 45 to 50 cu ft rule. 6 kW heaters rated for 170 to 300 cu ft cover it. A 6 kW heater draws 25 A; 125% is 31.3 A, so a 35 A 2-pole breaker with 8 AWG copper. Warm-up plus a 45 minute session uses about 6.3 kWh, $1.08, or about $14 a month at 3 sessions a week.
4 x 4 ft one-to-two person sauna, solid door
- 4 x 4 x 7 ft inside
- Solid wood door, no masonry
- 45 minute sessions, 3 a week
112 cu ft: a 4.5 kW heater on a 25 A circuit, about 81 cents a session.
112 cu ft is 2.2 to 2.5 kW by the rule of thumb, but the smallest 240 V heaters we list are 4.5 kW, rated from about 100 to 210 cu ft, so 4.5 kW is the fit. It draws 18.8 A; x 1.25 = 23.5 A, so a 25 A breaker with 10 AWG copper. About 4.7 kWh a session, or $10.54 a month.
7 x 6 ft basement sauna with two bare concrete walls
- 7 x 6 x 7 ft, 294 cu ft
- 40 sq ft of uninsulated concrete
- No glass
Size for 454 cu ft, not 294: a 9 kW heater on a 50 A circuit.
Harvia adds about 4 cu ft per sq ft of bare masonry, so the concrete adds 160 cu ft and the heater must cover 454 cu ft. That is a 9 kW heater rated past 450 cu ft. 9 kW at 240 V is 37.5 A; x 1.25 = 46.9 A, so a 50 A breaker, 8 AWG THHN or 6 AWG in NM-B cable. Insulating and paneling those walls would bring it back to a 6 kW heater.
Frequently asked questions
What size sauna heater do I need?
About 1 kW for every 45 to 50 cubic feet of sauna, then pick a heater whose maker range includes your room. Length x width x height gives cubic feet: a 6 x 5 x 7 ft room is 210 cu ft, which a 4.5 kW heater (up to about 210) only just covers and a 6 kW heater (about 170 to 300) covers with room to spare.
How does a glass door change the sauna heater size?
Glass and bare masonry lose heat, so Harvia adds 1.2 cubic meters of volume per square meter of that surface, about 4 cu ft per sq ft. A full glass door of about 12 sq ft adds about 48 cu ft, which can push a borderline room into the next heater size.
What size breaker does a 6 kW sauna heater need?
A 6 kW heater at 240 V draws 25 A. The NEC sizes fixed space heating circuits at 125% of the load, 31.3 A, so the next standard breaker is 35 A with 8 AWG copper. Some makers list 30 A with 10 AWG; your electrician follows the heater's installation manual and local code.
Can a sauna heater run on 120 V?
Only the smallest. 120 V heaters top out around 2 kW, enough for about 50 to 100 cu ft, and still draw about 17 A, so they need their own circuit. Anything 4.5 kW and up is 240 V.
How much does it cost to run a sauna?
Mostly the warm-up. A 6 kW heater running 40 minutes to heat up and about half the time during a 45 minute session uses about 6.3 kWh, roughly $1.08 at the US average of 17.3 cents. Three sessions a week is about $14 a month.
Do I need a contactor for my sauna heater?
Not with built-in controls: the thermostat and switching are in the heater. A heater run from a separate wall or Wi-Fi control switches through a contactor or power unit; packages like Amerec's SaunaLogic2 and Harvia's Cilindro with Xenio include it, so check the box contents before buying.
How many sauna stones does my heater need?
Whatever its maker specifies, and never run it empty. Heaters sold without stones list the fill: the VEVOR heaters take 22 to 33 lb and Mxmoonant 30 to 40 lb. Harvia KIP, Amerec, HUUM and Cilindro packages here include their stones.
Is it better to oversize a sauna heater?
Slightly, yes, within the maker's range: it heats faster and holds temperature with the door opening. Going below a heater's minimum room size is the mistake, since it overshoots and cycles off, and too small never reaches temperature.
Marcus Reed
Founder and Editor, CrunchYourDollars
Marcus Reed builds the sizing tools on CrunchYourDollars. He is a software engineer with a long-running PC hardware and power supply habit, which is where the watts, watt-hours and surge math on this site comes from. Product specs are pulled from manufacturer data sheets, electricity rates from the U.S. Energy Information Administration, and water chemistry rules from the Water Quality Association. He is not a licensed electrician or plumber: the tools show the math and the matching models so you can make the call, and anything involving your electrical panel should be checked by a licensed pro.
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