Home Sauna Size and Power Planner

Reviewed for 2026, updated September 8, 2026.

Estimates the interior footprint, floor space, heater size and electrical circuit a home sauna needs for the number of people who will use it together.

Your numbers

People using it at oncepeopleThe most people you expect to sit inside at the same time.Seating styleFacing benches split the group across two rows, which narrows the cabin but deepens it.Bench width per personinShoulder room allowed for each seated person.Interior ceiling heightinInside height of the cabin; lower ceilings heat faster and need a smaller heater.Heater watts per cubic footW/cu ftManufacturers publish their own sizing rule; 22 matches the common 1 kW per 45 cubic feet guideline for electric cabin heaters.Supply voltageMost small infrared cabins plug into 120 V; larger cabins and electric heaters need 240 V. Results update as you type.

Your estimate

Interior footprint (width x depth)...

Floor space to reserve...

Heater size...

Minimum circuit...

Estimates only. Assumptions are listed below, and you can change every input.

A frequent regret among home sauna owners is buying a cabin that is one seat too small, and another is discovering that the heater it needs cannot run from the outlet in the spare room. Product pages describe cabins as two-person or four-person without saying how wide the benches are or what the electrician will have to install.

This planner starts from the number of people and the seating style you want, allows a bench width per person and returns an interior footprint, the floor area to reserve once walls and an air gap are added, and the cabin volume. It then sizes the heater from that volume using the watts per cubic foot you enter and converts it to a minimum circuit size at 120 or 240 volts using the standard 80 percent continuous load rule. Use it to shortlist cabins and brief an electrician, then confirm against the manufacturer’s own chart and local code.

How to use this tool

Enter how many people will use the sauna at the same time and choose the seating style you prefer.
Set the bench width per person and the interior ceiling height, and keep or change the watts per cubic foot to match your chosen manufacturer.
Pick the supply voltage available where the sauna will go, then read the footprint, floor space, heater size and minimum circuit.

What the math assumes

Cabin depth (bench plus foot room) is fixed at 42 in for upright seating, 72 in for a reclining lounger and 84 in for two facing benches. Adjust the bench width per person if your builder’s plans differ.
Interior width never drops below 36 in when at least one person is seated, so the door can swing and an adult can turn around.
Heater watts scale linearly with cabin volume using the watts per cubic foot you enter. The 22 W default is rounded from the 1 kW per 45 cubic feet guideline commonly published for electric cabin heaters; check your manufacturer’s chart and round up to the next model they actually make.
The circuit size applies the 80 percent continuous load rule (watts divided by volts divided by 0.8) and rounds up to the next standard breaker size. A licensed electrician makes the final call and local code governs.
Floor space adds 6 in on every side for wall thickness and an air gap. Outdoor kits, glass fronts, roof overhangs and door swing need more.

Frequently asked questions

Why is the heater size different from what the cabin manufacturer lists?

Manufacturers size heaters for their own wall construction, glass area and target temperature, and they only make a handful of models. Treat this planner as a sanity check and round up to the closest heater the maker recommends for that cabin.

Can a home sauna really run from a normal 120 V outlet?

Small infrared cabins with modest wattage often can, which is why the planner offers 120 V. Once the minimum circuit climbs past 15 or 20 A at 120 V, a dedicated 240 V circuit is almost always the safer and more practical answer.

How much extra room should I leave around the cabin?

The floor area figure already adds 6 in on each side for walls and an air gap, but it does not include door swing, a step or a bench outside. Sketch the room with those items before ordering.

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