How many calories do you burn in a sauna?

How many calories does a sauna burn?

Fewer than most sites say, and more than zero. Sitting in heat does raise your metabolic rate, but few studies report by how much, and the two this calculator uses put the rise at roughly 25–80% above rest — one in a sauna, one in hot water.

• In a Finnish study of ten men taking an hour at 80°C twice a day for a week, metabolic rate increased by 25–33% “after the first day” (Leppäluoto et al., 1986). The abstract does not say how or exactly when it was measured, and we could not get the full paper.
• In a Loughborough study, an hour sitting in 40°C water raised energy expenditure by 61 kcal an hour — 79% over rest — measured by indirect calorimetry. Moderate cycling in the same study added 556 kcal an hour (Faulkner et al., 2017). Hot water heats you faster than sauna air does, so that is the generous end.

In the units the Compendium of Physical Activities uses, where sitting quietly is 1 MET (about 1 kcal per kilogram per hour), that makes a sauna roughly 1.25–1.8 METs. The Compendium itself has no sauna entry; its nearest, sitting in a whirlpool, is 1.3 METs. Walking at an ordinary 2.8–3.4 mph is 3.8. So for 180 lb, 30 minutes in the sauna is about 50–75 kcal, of which 10–35 is extra over sitting still — and the same half hour walking is about 155.

Why the big numbers are wrong

Omni Calculator says a person burns “about 500 kcal” sitting in a sauna for an hour. A Crunch blog post says an infrared sauna burns “300-690 calories in a 40-minute session”. At 30 minutes those work out to 250 and 225–520 kcal — more than a 180 lb person burns walking for the same half hour, from sitting down, and several times any value measured by gas analysis.

Your watch probably agrees with them, and that is the clue: it works out calories from your heart rate. In a sauna your heart rate climbs — by about 60% at 80°C and 90% at 100°C in one Finnish study (Kukkonen-Harjula et al., 1989) — but the extra blood is going to your skin to shed heat, not carrying oxygen to working muscle. When a Polish team fitted young women with heart-rate monitors, the monitors credited them with about 119 kcal for 20 minutes at 80°C (Podstawski et al., 2023). For their average weight of 59 kg, the range above comes to about 25–35 kcal, less than a third of that.

Calories burned in a sauna for 10, 15, 20, 30, 45 or 60 minutes

The same model worked out for two body weights in a Finnish sauna at 80°C (176°F). Sessions over 20 minutes are split into rounds with short cool-downs, which is how people actually use a sauna and how most of the studies ran them. Put your own weight and session into the calculator for anything else.

Two things stand out. The calories barely move — a whole hour at 180 lb costs about what a 20- to 30-minute walk does — while the sweat climbs fast. And the sweat is the only column the scale sees.

Infrared vs Finnish vs steam: does the type matter?

For calories, we found no study comparing the types directly, so this calculator does not invent a difference between Finnish and steam. Infrared is the exception, because its temperature decides whether it heats your core at all.

• Finnish (dry) sauna. Usually 80–100°C at 10–20% humidity, in rounds of 5–20 minutes (Hussain & Cohen, 2018). Most of the research is on this kind. Thermostats can flatter: in a University of Oregon study, a sauna whose thermostat showed 78°C measured 66°C on a separate sensor (Atencio et al., 2025).
• Infrared. Usually run at 45–60°C. At about 45°C a 45-minute session left core temperature unchanged and cost people 0.48% of body weight (Reed et al., 2025). At 65°C the same length of session raised rectal temperature 1.4°C, pushed heart rate from 74 to 153 beats a minute and took off 1.5% of body weight (Jenkins et al., 2026). As for the claim that infrared reaches 3–4 cm into muscle, probes in the thigh found the warming had lessened by 63% at 2.4 cm deep, and the authors concluded commercial infrared saunas heat only superficial tissue (Reed et al., 2025).
• Steam room. Cooler, very humid air. In the same ten men, a 59°C bath at about 60% humidity took off half the body mass of a 91°C dry sauna (0.36 kg against 0.72 kg) yet raised rectal temperature and heart rate more, because sweat cannot evaporate in wet air (Pilch et al., 2014). A smaller scale drop after steam does not mean an easier session.

How much weight do you lose in a sauna?

Typically a pound or two, and almost all of it is water. Measured losses from sessions like the ones this page models:

• 0.37 kg for women and 0.50 kg for men after two 10-minute rounds at 90°C, in 674 students — with larger bodies losing more (Podstawski et al., 2014).
• 0.72 kg after three 15-minute rounds at 91°C (Pilch et al., 2014).
• 0.65 kg after four 10-minute rounds at 90°C (Podstawski et al., 2019).
• 0.7–0.9 kg after an hour at 80°C (Leppäluoto et al., 1986).

A kilogram of body mass lost in a sauna is roughly a litre of sweat. The fat side of the ledger is tiny: 50–75 kcal is at most 9 g of fat even if every calorie came from fat, which it does not. Drink the water back and the scale goes back with it.

How much water to drink after a sauna

After exercise, the guidance for replacing a large deficit quickly is to drink 1.25–1.5 litres for every kilogram lost (roughly 19–23 oz per pound). The American College of Sports Medicine’s 2007 position stand suggests about 1.5 litres a kilogram for rapid, complete recovery; the 2016 joint position of the ACSM, the Academy of Nutrition and Dietetics and Dietitians of Canada gives 1.25–1.5 litres, for big deficits you need to fix within 12 hours (as summarised by McCartney et al., 2017). For small losses and when there is time, normal meals and drinks do the job. The target is more than you lost because some of what you drink becomes urine. In one trial, drinking more than the loss only restored fluid balance when the drink carried enough sodium; with a low-sodium drink the extra mostly came out again (Shirreffs et al., 1996).

For 180 lb and 30 minutes at 80°C that is about 17–21 oz (0.51–0.61 L) — a couple of glasses, spread over two hours if you want to square it quickly. For a single short round, your normal drinking covers it. If you want to check your own loss rather than trust an estimate, weigh yourself before and after and use the sweat rate calculator; for the rest of the day, the water intake calculator gives you a baseline to add it to.

Electrolytes after a sauna

Sweat takes sodium with it, and how much you need back depends on how much you lost. After one or two short rounds, water and your next meal are enough. After long or repeated sessions, it is worth thinking about:

• Men doing an hour at 80°C twice a day showed falling blood sodium and potassium by day three, and the authors flagged electrolyte balance for “long-lasting intense heat exposure” (Leppäluoto et al., 1986).
• Extra fluid that is low in sodium largely ends up as urine (Shirreffs et al., 1996).
• Food does the job well. Plain water with an ordinary meal restored fluid balance better than a sports drink, which the authors suggested may be down to the extra sodium and potassium the meal brought (Maughan et al., 1996).

So a salty meal and water is a perfectly good recovery drink. If you want to know what the sports drinks actually contain and do, the sports drinks page in our hydration guide goes through the trials.

Is it safe to use a sauna when you’re dehydrated?

It is a bad idea. A sauna takes water out and lowers blood pressure — the diastolic reading fell by 7–37 mmHg in Leppäluoto’s men and by 15–20 mmHg in Pilch’s — and starting already short on fluid only adds to both. The NHS lists people who are already ill and dehydrated, from diarrhoea or vomiting, among those most at risk in heat. Alcohol adds to the blood-pressure problem: the classic review of sauna risks singles out drinking alcohol during a sauna as the thing to avoid (Hannuksela & Ellahham, 2001).

In the 120°C study, vomiting came directly before two of the three faints (Podstawski et al., 2023). Dizziness, nausea and vomiting are among the heat-exhaustion symptoms that study screened for. Any of them means get out, sit down somewhere cool, and drink.

Should you drink water in the sauna?

Between rounds, yes, if you want to. Some of the studies above let people drink during the session — the infrared recovery study had them drink 500 mL over 30 minutes (Mero et al., 2015) — and it is the same logic as drinking during exercise: finishing less far behind. The ACSM puts the line for too far behind at 2% of body weight. Two of twelve people in the 65°C infrared study crossed it in a single 45-minute session (Jenkins et al., 2026).

How this calculator works

• Calories: 1.25–1.8 METs × body weight in kg × hours in the heat. For infrared, the range slides from 1.0–1.25 METs at 45°C up to the full range at 65°C, because the cool end barely warms the core. That interpolation is ours, not a published formula. Cool-downs are counted at the cost of sitting.
• Sweat: a percentage of body mass per hour of heat, adjusted for temperature. For a Finnish sauna it is anchored at 1% an hour at 80°C. Five sessions at 80–91°C lost 0.7–1.9% an hour; brought to 80°C with the temperature slope, they average about that. They are two at 80°C (Podstawski et al., 2023; Leppäluoto et al., 1986, whose 0.7–0.9 kg an hour is roughly 0.8–1.3% for men of 70–90 kg — the abstract gives no weights) and three at 90–91°C (Podstawski et al., 2014 and 2019; Pilch et al., 2014). Infrared is anchored at 0.65% at 45°C and steam at 0.6% at 59°C. The Finnish slope (about 3% more sweat per degree) comes from a single study comparing 80°C with 120°C, so below 80°C it is extrapolated; steam borrows it because only one controlled study has measured steam. The infrared slope comes from the 45°C and 65°C studies, which differ by a factor of three.
• How far to trust it: as a rough guide. Studies at similar temperatures scatter widely, and the two that measured the air with their own sensors found more than this model gives below 80°C — about 0.8% an hour at 60°C (Laatikainen-Raussi et al., 2026) and about 1.7% at 66°C, counting what people drank (Atencio et al., 2025). People in the same study differ too: 1.4 ± 0.5 litres an hour in the 65°C infrared study (Jenkins et al., 2026). So the range shown runs from 50% to 200% of the middle estimate — half to double — and it is a typical range, not a limit. Weighing yourself before and after is the only reliable figure.
• Drink-back: 1.25–1.5 times the middle sweat estimate, spread 30/25/25/20% over two hours. The split is a practical choice, not a published protocol.
• Caps: 20 minutes a round for Finnish and steam, 45 for infrared, and 60 minutes of heat in total. The calculator will not model anything longer.

Sources

1. Faulkner SH et al. The effect of passive heating on heat shock protein 70 and interleukin-6. Temperature, 2017.
2. Leppäluoto J et al. Some cardiovascular and metabolic effects of repeated sauna bathing. Acta Physiologica Scandinavica, 1986.
3. Herrmann SD et al. 2024 Adult Compendium of Physical Activities. Journal of Sport and Health Science, 2024 (codes 07021, 02135, 17190).
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5. Podstawski R et al. The influence of extreme thermal stress on the physiological and psychological characteristics of young women who sporadically use the sauna. Frontiers in Public Health, 2023.
6. Podstawski R et al. Sauna-induced body mass loss in young sedentary women and men. The Scientific World Journal, 2014.
7. Podstawski R et al. Correlations between repeated use of dry sauna for 4 × 10 minutes, physiological parameters, anthropometric features, and body composition in young sedentary and overweight men. BioMed Research International, 2019.
8. Pilch W et al. Comparison of physiological reactions and physiological strain in healthy men under heat stress in dry and steam heat saunas. Biology of Sport, 2014.
9. Atencio JK et al. Comparison of thermoregulatory, cardiovascular, and immune responses to different passive heat therapy modalities. American Journal of Physiology — Regulatory, Integrative and Comparative Physiology, 2025.
10. Reed EL et al. Muscle temperature increases during a single far infrared sauna session without changes in intestinal temperature. Journal of Applied Physiology, 2025.
11. Jenkins EJ et al. Far-infrared sauna exposure at 65°C elevates core temperature. Experimental Physiology, 2026.
12. Laatikainen-Raussi I et al. Temperature and humidity independently influence thermoregulatory responses during Finnish sauna bathing. Temperature, 2026.
13. Mero A et al. Effects of far-infrared sauna bathing on recovery from strength and endurance training sessions in men. SpringerPlus, 2015.
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19. Shirreffs SM et al. Post-exercise rehydration in man: effects of volume consumed and drink sodium content. Medicine & Science in Sports & Exercise, 1996.
20. Maughan RJ et al. Restoration of fluid balance after exercise-induced dehydration: effects of food and fluid intake. European Journal of Applied Physiology, 1996.
21. Jones EJ et al. Effects of metered versus bolus water consumption on urine production and rehydration. International Journal of Sport Nutrition and Exercise Metabolism, 2010.
22. Kovacs EM et al. Effect of high and low rates of fluid intake on post-exercise rehydration. International Journal of Sport Nutrition and Exercise Metabolism, 2002.
23. NHS. Heatwave: how to cope in hot weather (reviewed June 2026).
24. FAO. Food energy — methods of analysis and conversion factors, chapter 3 (Atwater factors), 2003.
25. Omni Calculator. Sauna calories burned calculator (quoted as checked on 25 September 2026).
26. Crunch. Does an infrared sauna burn calories? Facts and myths (quoted as checked on 25 September 2026).

Last reviewed 25 September 2026.