Thermoregulation calculator theory
The thermoregulation calculator estimates how the body balances heat production and heat loss during activity. It uses ambient temperature, humidity, exercise intensity, clothing, airflow, sweat rate, hydration, and heat acclimation to build an educational heat-balance model.
Core heat-balance idea
The body gains heat mainly from metabolic heat production during exercise. It loses heat through dry heat exchange, such as radiation and convection, and through evaporative cooling from sweat. The simplified balance is:
\[
\begin{aligned}
H_{storage} &= H_{production} - H_{dry} - H_{evaporation}
\end{aligned}
\]
If heat production is greater than heat loss, net heat storage is positive and body heat accumulation becomes more likely. If heat loss is equal to or greater than heat production, the model shows heat balance or cooling surplus.
Evaporative cooling depends strongly on humidity. Sweat only cools effectively when it evaporates. In the calculator, sweat cooling potential is estimated from sweat rate:
\[
\begin{aligned}
H_{sweat,potential} &= \text{sweat rate} \cdot 674
\end{aligned}
\]
The value 674 W per L/h is a teaching approximation for the cooling power of sweat evaporation. The calculator then reduces this potential using humidity, airflow, clothing, hydration status, and acclimation factors.
How to interpret the result
A high evaporation effectiveness means sweat can remove heat efficiently. A low evaporation effectiveness means sweat may remain on the skin instead of evaporating, which is common in humid conditions or when airflow is poor.
Dry heat exchange depends on the difference between skin temperature and air temperature. When air temperature approaches or exceeds skin temperature, radiation and convection become much less helpful and may even add heat instead of removing it.
The heat-stress risk category is a teaching score, not a clinical diagnosis. Risk rises when metabolic heat production is high, humidity is high, airflow is poor, clothing is heavy, hydration is reduced, acclimation is low, or exercise duration is long.
Common pitfalls
Do not treat the result as a medical clearance tool. Real heat risk also depends on illness, medications, sleep, fitness, sun exposure, work-rest cycles, protective equipment, and individual heat tolerance.
Micro example: if metabolic heat production is 520 W, dry heat loss is 20 W, and evaporative cooling is 300 W, then \(H_{storage} = 520 - 20 - 300 = 200\) W. This means heat is accumulating in the teaching model.
Use this calculator to explore how changing humidity, clothing, airflow, sweat rate, and intensity changes heat balance. For symptoms such as confusion, fainting, severe dizziness, collapse, or suspected heat illness, seek urgent professional care.
