Wet-Bulb Temperature Calculator
Enter the dry-bulb air temperature and relative humidity to calculate wet-bulb temperature, dew point, and a heat-stress category. The calculator uses the Stull (2011) empirical formula, accurate to ±0.3°C across the normal environmental range.
Temperature unit
°C
%
Stull (2011) empirical formula — valid −20°C to 50°C, RH 5–99%
How does this calculator work?
Wet-bulb temperature (Tw) uses the Stull (2011) formula: Tw = f(T, RH) where T is dry-bulb temperature and RH is relative humidity (%). Tw always falls between dew point (Td) and T. At RH = 60% and T = 30°C, Tw ≈ 24.0°C — dangerous conditions occur when Tw exceeds 28–31°C.
Formula
How this is calculated
The wet-bulb temperature (Tw) is the lowest temperature achievable by evaporative cooling — it is what a thermometer covered in a wet wick reads when air passes over it. Unlike the dew point (the temperature at which air becomes saturated), the wet-bulb temperature depends on both the ambient temperature and the humidity, and it sits between the dew point and the dry-bulb temperature: Td ≤ Tw ≤ T. When relative humidity is 100%, all three values are equal.
This calculator uses the Stull (2011) empirical regression formula (Journal of Applied Meteorology and Climatology, 50(11), 2267–2269), which is accurate to within ±0.3°C for −20°C ≤ T ≤ 50°C and 5% ≤ RH ≤ 99%. It avoids the need for iterative psychrometric equations and is widely used in meteorological and occupational health applications. The dew point is derived separately using the Magnus formula (Lawrence 2005 approximation), accurate to < 0.35°C over the same range.
Heat stress categories are based on the wet-bulb temperature alone (an indoor WBGT proxy). Outdoor heat stress also incorporates solar radiation via the Wet Bulb Globe Temperature (WBGT), which requires a separate black-globe thermometer reading. The spread between dry-bulb and wet-bulb (T − Tw) indicates aridity: a large spread means dry air with high evaporative cooling potential; a small spread means humid conditions where sweating is less effective.
Frequently asked questions
The human body cools itself primarily through sweat evaporation. When the wet-bulb temperature approaches body temperature (~35°C or 95°F), evaporation becomes ineffective even for fit, unclothed individuals at rest in the shade. Sustained wet-bulb temperatures above ~31–32°C are dangerous without air conditioning. A 2020 study (Sherwood & Huber) set a theoretical survivability limit of Tw = 35°C.
The dew point is purely a function of moisture content — it is the temperature at which the air would become saturated if cooled at constant pressure. The wet-bulb temperature also depends on the current temperature because evaporation rate is linked to the vapour pressure deficit. The wet-bulb is always between the dew point and the dry-bulb temperature.
Wet Bulb Globe Temperature (WBGT) combines the wet-bulb temperature (70% weight), a black-globe thermometer reading of radiant heat (20%), and ambient dry-bulb temperature (10%). It is the standard metric for occupational and athletic heat stress assessment. The simple wet-bulb temperature calculated here is equivalent to WBGT only indoors with no solar load.
Also known as
TG we-Calculate Editorial Team. (2026). Wet-Bulb Temperature Calculator [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/wet-bulb-calculator
TG we-Calculate Editorial Team. "Wet-Bulb Temperature Calculator." TG we-Calculate. 2026. https://we-calculate.com/calculator/wet-bulb-calculator.
TG we-Calculate Editorial Team, "Wet-Bulb Temperature Calculator," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/wet-bulb-calculator
@misc{wecalculate_wet_bulb_calculator, title = {Wet-Bulb Temperature Calculator}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/wet-bulb-calculator}}, year = {2026}, note = {TG we-Calculate} }
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