Recovery calculator
Sauna calculator — which group of the Finnish cohort you fall in
Enter how often you use a sauna, for how long, and how hot. The page tells you which group of the Kuopio cohort study you would have been counted in — not what you should be doing. Free, instant, no sign-up.
This is the group the study counted you in, not a rating. The groups are named for their frequency and nothing else.
Where heat sits around your training week is a real question. What it does to your mortality risk is not one a calculator can answer.
What this calculator actually returns
A group, not a score. It reports which frequency band of the Kuopio Ischaemic Heart Disease study your habit would have placed you in, alongside whether your sessions clear the duration mark the same cohort reported and whether your sauna runs at the temperatures the cohort describes. There is no target here, no rating, and no recommendation, because the underlying evidence does not support one.
The Kuopio study
Laukkanen and colleagues published the analysis in JAMA Internal Medicine in 2015: 2,315 middle-aged Finnish men followed for a median of 20.7 years. The finding was a clear dose-response. Compared with one session a week, four to seven sessions was associated with substantially lower all-cause and cardiovascular mortality over two decades, and within a frequency band, sessions longer than nineteen minutes were associated with lower risk than shorter ones. Later work from the same cohort reported similar gradients for dementia and respiratory disease.
Why this is not a prescription
The study is observational, so the arrow could point either way — and here it plausibly does. Taking seven saunas a week requires being well enough to take seven saunas a week, which makes frequency a marker of health as much as a cause of it. The confounder is severe rather than theoretical. It is also worth being clear about who was studied: every participant was a middle-aged Finnish man in a country where sauna use is near-universal, so the reference group is not "normal people" but "Finns who barely sauna" — an unusual group, for reasons that may themselves matter.
80 to 100 °C, or something else entirely
The Finnish sauna the cohort describes runs at 80 to 100 °C. This page checks your temperature against that range and says so when you are outside it, because the alternative is quietly treating an infrared cabin, a steam room or a warm home unit as the thing that was studied. They may well do something. They were not what was observed in Kuopio.
Where the calculator stops
It stops at the band. It will not give you a number to beat, because the study reported groups rather than an optimum, and stacking more heat on because a chart went up is not what the data says. The entry limits reflect the same caution at the other end: an hour is the longest session this page will take, on the grounds that beyond an hour in a hot room is not a protocol but a hazard.