The 200 rule for saunas is a general guideline stating that the sauna temperature (in °F) plus the relative humidity percentage should add up to roughly 200 for a balanced, comfortable session.

The 200 rule helps users calibrate the relationship between dry heat and moisture — two variables that dramatically affect how intense a sauna session feels. A traditional Finnish-style sauna at 180°F, for example, calls for around 20% humidity to hit 200. A lower-temperature far infrared sauna running at 130–140°F operates outside this framework entirely, since far infrared cabins rely on radiant panel heat rather than air temperature and humidity balance — the 200 rule applies specifically to traditional dry and wet sauna environments.

  • The 200 rule target: temperature (°F) plus relative humidity (%) equals approximately 200.
  • Traditional Finnish sauna example under the 200 rule: 180°F + 20% humidity = 200.
  • Lower-humidity example: a 160°F dry sauna paired with roughly 40% humidity also satisfies the 200 rule.
  • Far infrared saunas operate at 104–140°F and do not use humidity, placing them outside the 200 rule's scope.
  • The 200 rule is a comfort guideline, not a safety standard — no regulatory body formally enforces it.