Home Sauna Size Calculator

How to use the sauna size calculator

1. Say how many people will use it at once, from one to six.
2. Measure the space: the corner of a basement, a spare room or a garage bay, and its ceiling height. Building your own room? Enter the room’s inside size instead.
3. You get the smallest indoor sauna sold for that many that fits, its inside and bench sizes, the heater and circuit it needs, every other model for that many people (✓ fits, ✗ does not), and the heater a room built in your space would take, drawn from above to scale.

Planning a hot tub as well? The hot tub size calculator fits a tub to your spot and your deck.

The rules, and where they come from

The saunas. Almost Heaven prints, for each indoor model, the people it holds, its “Exterior dimensions”, “Interior dimensions” and “Bench dimensions”, and its heater: “Heater size: 6kW, 240V, 30-amp requirement, hard-wire connect”. Its 8 kW heaters need 40 A and its 9 kW 45 A; the light runs on an ordinary 110 V, 15 A outlet.

The heaters. Harvia’s US product pages give each heater a room volume: the KIP60B (6 kW) “169 – 300 ft³”, the KIP80B (8 kW) “251 – 424 ft³”, the KIP90 (9 kW) “283 – 494 ft³”. The KIP60 data sheet asks for a room at least 1,900 mm (6′3″) high; the KIP80 and KIP90, 2 m (6′7″).

Glass and stone. Harvia: “The power requirement increases if there are window surfaces or heat-storing surfaces such as brick, concrete or massive logs in the sauna.” Its sauna volume calculator adds a glass door and non-insulated walls to the volume.

Kits and heaters. Almost Heaven puts a heater one size above Harvia’s range for the inside volume in every kit: its one- to three-person saunas are 69–140 ft³ inside and carry a 6 kW heater. A kit is designed and sold as a set. For a room you build, size the heater by the heater maker’s range.

The indoor saunas, size by size

From almostheaven.com, 5 October 2026. Inside volume is the inside width × depth × height. Most benches are about 24″ deep and 36–38″ high.

Harvia’s heaters and the room they heat

Worked examples

A 2-person sauna: Almost Heaven’s Hillsboro, 63″ × 45¼″ outside: a 6′ × 7′ basement corner with an 8′ ceiling. The Spectacle, Auburn and Madison fit too; the Hillsboro takes the least floor.

A 4-person sauna: Almost Heaven’s Rainelle, 71½″ × 62¾″ outside: in a 6′ × 6′ space it fits with half an inch to spare, and so does the square Grayson. The Oasis and Worthington are too long.

A 6-person sauna: Almost Heaven’s Worthington, 81⅞″ × 64¼″ outside: a 7′6″ × 8′ room fits every six-person model; the Worthington takes the least floor.

No 4-person sauna kit fits your 5′ × 5′ space: the smallest for four is 71½″ long. A room built to 5′ × 5′ × 8′ is 200 ft³, inside a 6 kW heater’s range.

Common mistakes

• Forgetting the ceiling. Kits stand 77⅝–80⁵⁄₁₆″ tall outside: a low basement ceiling can stop one that fits the floor.
• Planning on a plug. The heater is hard-wired on 240 V; only the light plugs in.
• Sizing the heater by the floor alone. Harvia sizes by volume, and glass, brick and concrete raise the power needed.
• Counting the bench as seats. A model’s people count is the maker’s; the bench length per person varies by design.

More on spa rooms at Dreamy Home Style

• Sauna aesthetic ideas for your home
• The sauna and hot tub fix
• Spa-like bathroom ideas
• Scandinavian bathroom ideas
• Wood bathroom ideas

Fitting it into a basement or a bathroom? Draw the room to scale in the free 2D floor planner.