Sauna Session Planner

Sauna use reduces cardiovascular mortality risk, improves heat shock protein production, and raises growth hormone. The dose is measured in temperature, duration, and frequency.

Types of sauna

Finnish dry sauna operates at 80-100C (176-212F) with 10-20% relative humidity. This is the most studied type. Most cardiovascular and mortality-reduction research comes from Finnish sauna populations using 80-90C for 15-20 minutes, 4-7 times per week.

Steam rooms operate at 40-60C (104-140F) but near 100% humidity. Sweat does not evaporate in steam, so the body heats faster for a given air temperature. The perception of heat is much stronger.

Infrared saunas operate at 45-65C (113-149F) and heat tissue directly rather than heating the air. Despite lower air temperatures, core temperature rises similarly to traditional saunas over longer sessions (30-45 minutes).

Session duration guidelines

The practical limit is when your heart rate climbs past about 75% of your maximum, or when you feel dizzy, nauseous, or lightheaded. Most healthy adults reach that in 15-25 minutes in a 90C Finnish sauna.

A conservative approach: start at 80C for 8-10 minutes, exit, cool for 5-10 minutes, repeat 1-2 rounds. Total heat exposure per session: 15-30 minutes.

How this calculator sets the numbers

Each sauna type has a reference temperature with a known comfortable ceiling for an experienced user, and the ceiling moves as the temperature does:

Steam falls off fastest per degree because sweat cannot evaporate at 100% humidity, so the body loses its main cooling route. Infrared runs longest because the air stays cool enough to breathe comfortably while radiant energy does the heating.

Experience then scales the ceiling: a beginner gets half, someone one to six months in gets three quarters, and an experienced user gets all of it. The recommended round is 75% of the ceiling, which is where you want to be sitting rather than the edge you should not cross.

Run the numbers for 80C dry as a beginner and you get 9 minutes, which is exactly the 8-10 the paragraph above recommends. That is not a coincidence: the table was fitted to it.

Heart rate. The 150 bpm figure you see quoted everywhere is a bad universal rule. It is roughly 79% of maximum for a 25-year-old and about 94% for a 70-year-old, so the same number is relaxed for one and genuinely risky for the other. This calculator uses 208 − 0.7 × age for maximum heart rate (Tanaka) and puts the exit threshold at 75% of it.

Hydration. Sweat rate in a 90C sauna is roughly 500-1000 mL per hour. Drink 400-600 mL of water before and replace after. Sports drinks are not necessary unless you are doing multiple long sessions.

Alcohol before a sauna is the single most dangerous combination here, and it accounts for a large share of the sauna deaths recorded in Finland. It blunts the thirst signal, impairs the judgment you need to decide when to leave, and drops blood pressure at the same time the heat is already dropping it.