Buying
What size sauna do I need?
Sixty centimetres of bench per seated adult, 1.8m to lie down. The number on the listing is the most misleading figure in the category.
Capacity claims in this industry are optimistic, and the gap between the number on the listing and the number of people who fit comfortably is where most buyer's remorse lives. The fix is to stop reading capacity as a headline and start measuring bench length, because a bench is the only thing a sauna actually gives you.
The two numbers that decide it
Allow 60cm of bench per seated adult, and 1.8m of bench for one person lying down. Everything else follows from those two figures.
| Claimed capacity | Typical footprint | Real seated | Anyone lying down? |
|---|---|---|---|
| 2 person | 1.15m × 1.15m | 2 upright, shoulder to shoulder | No |
| 2-3 person | 1.2m × 1.5m | 2 comfortably, 3 at a squeeze | No |
| 3-5 person | 2m × 2m | 4 comfortably | Yes, one person |
| 6-8 person | 2.5m × 2.4m | 6 comfortably | Yes, two people |
A cabin sold as two person seats two adults upright with shoulders touching and no room to stretch out. That is not a defect, it is what the footprint allows. If lying down matters to you, the entry point is a cabin sold as three to five person, which is a different price bracket and a different planning conversation.
Two benches or one
Above about 1.9m square, most cabins offer an L-shaped or two-tier bench layout, and it changes the room more than the extra floor area does. A second tier gives you a genuine temperature choice, because the air near the ceiling can be 20°C hotter than at knee height. In a single-bench cabin you get one temperature and that is the sauna.
For households where one person wants 90°C and another finds 70°C plenty, a two-tier bench solves an argument that no amount of thermostat fiddling will. That alone justifies sizing up one step for a lot of families.
Height is the constraint that rules rooms out
Indoor cabins need roughly 210cm of ceiling. Below that the cabin will not stand, which is what pushes plenty of buyers into a garage or the garden before they have chosen anything else. Measure the room's lowest point, not its highest, and remember that a loft conversion also needs a floor loading opinion before a 200kg to 400kg cabin goes into it.
Outdoors, height works the other way: the Planning Portal's outbuilding rules cap a garden building at 2.5m when it sits within 2m of a boundary, which is why so many are built at 2.1m to 2.2m. Ground preparation is the other half of that decision, and getting the base right before the cabin arrives matters more at larger sizes, because weight climbs fast.
Sizing up is cheaper than it looks
Within a single product range, the jump between sizes is small relative to the base price. Moving from a 1,150mm square shell to a 1,505mm square one is roughly £600, which is a fraction of the cost per extra person that the capacity labels imply. The expensive jumps are between ranges and between indoor and outdoor, not between adjacent sizes.
The cost that does scale with size is the heater, because output is set by cubic metres. A bigger cabin needs a bigger heater and sometimes a heavier circuit certified under Approved Document P, so the honest comparison is shell plus heater plus circuit, and matching heater output to cabin volume is what fixes the middle number. Running cost follows the same curve at Ofgem's current unit rate, and the per-session figures sit in what a sauna costs to run.
Buy for the session you will actually have
The most common sizing mistake is buying for the largest gathering you can imagine rather than the routine you will keep. A two-person cabin used four evenings a week beats a six-person cabin used monthly: it is cheaper to heat, quicker to get into, and it fits a room you already have. Past eight seats the panel-built market thins out and you are into commissioned builds, which is a different budget entirely and where our luxury sauna rankings start.
Count the people who will realistically be in it at the same time, decide whether anyone needs to lie down, then pick the smallest cabin that satisfies both. That is the third of the six decisions in choosing a home sauna, and once it is settled the shortlist on our outdoor sauna rankings shortens to two or three entries.
Frequently asked questions
What size sauna do I need for 2 people?
About 1.15m square as a minimum, which seats two adults upright shoulder to shoulder. If you want either person to be able to lie down, you need a bench of about 1.8m, which means a cabin sold as three to five person.
How much bench space does one person need?
Around 60cm of bench width to sit comfortably, and about 1.8m of length to lie down. Those two figures are more reliable than any capacity claim on a product listing.
What ceiling height does a sauna need?
About 210cm for an indoor cabin, measured at the lowest point in the room. Cabins stand roughly 200cm tall and need clearance above for ventilation and assembly.
Is a 2-person sauna big enough for a couple?
For sitting, yes, and for regular evening use it is often the right choice because it heats fast and fits in a spare room. It is not big enough if either of you wants to lie down or if guests will ever join.
How much does it cost to size up?
Within a range, roughly £600 a step, so moving from a 1,150mm square shell to a 1,505mm one is comparatively cheap. The real cost of sizing up is the larger heater and possibly a heavier circuit.
What size sauna fits in a garage?
Most standard garages take a two to four person cabin comfortably, since ceiling height is usually fine and the floor is already concrete. Measure the door opening as well, because panels have to get in.
Do I need a two-tier bench?
Only above about 1.9m square, and only if people in your household disagree about heat. The upper bench can sit 20°C hotter than the lower one, which lets two people share a session at different intensities.
How many people fit in a barrel sauna?
Fewer than the length suggests, because the curve removes shoulder room at both ends. A barrel rated for four seats four only if nobody is sitting right at the ends.
What is the smallest practical sauna?
About 1m square for a single person seated, and an infrared blanket below that if there is no floor space at all. Below 1.15m square, two people is not a realistic claim.
Should I buy bigger for resale?
No. A sauna is very hard to move and does not have a meaningful resale market, so size it for your own use. Buying larger for a hypothetical future buyer costs you running cost every session in the meantime.