What this calculator does

This wet-bulb temperature calculator estimates the temperature air can reach through evaporative cooling at a given temperature and humidity. Wet-bulb temperature is important in meteorology, cooling processes, and heat-stress interpretation because it links temperature with the evaporative capacity of the air.

When the air is dry, evaporation is efficient and wet-bulb temperature sits much lower than air temperature. When the air is already moisture-laden, evaporation becomes less effective and wet-bulb temperature climbs closer to the dry-bulb value. That relationship helps explain both cooling performance and some forms of environmental heat stress.

Inputs explained

• Air temperature: Enter the dry-bulb air temperature used as the starting condition.
• Relative humidity: Enter the moisture state of the air as a percentage.
• Internal unit handling: The Stull approximation is evaluated in Celsius inside the engine and the page reports both C and F outputs.

How it works / method

The calculator uses Roland Stull's compact empirical wet-bulb approximation. It is a practical shortcut for standard near-sea-level atmospheric pressure and is widely used for quick estimation when a full psychrometric or iterative solution is unnecessary. The method is especially useful when you need an online estimate from only temperature and relative humidity.

Formula used

This is the Stull 2011 approximation for standard atmospheric pressure. It is a fit, not a full thermodynamic solver, so it is best treated as a practical estimate rather than an exact psychrometric reference value.

Step-by-step example

Suppose the air temperature is 32 C and the relative humidity is 50 percent. The wet-bulb value helps show how much evaporative cooling is still available.

1. Enter 32 for air temperature.
2. Enter 50 for relative humidity.
3. The page estimates a wet-bulb temperature near the mid 20s C.
4. That gap between dry-bulb and wet-bulb temperature reflects the cooling that evaporation can still produce.
5. If humidity rises further, the wet-bulb result climbs and the available evaporative relief shrinks.

Use cases

• Checking whether evaporative cooling methods are likely to be effective in a given weather pattern.
• Comparing humid heat events where dry air temperature alone understates environmental strain.
• Supporting psychrometric interpretation in classrooms, field notes, and quick engineering estimates.
• Providing an input or comparison point for broader heat-stress discussions and related tools such as WBGT.

Assumptions and limitations

• This page uses an approximation that assumes standard atmospheric pressure and is not a universal replacement for full psychrometric methods.
• Results become less reliable outside the validated range described in the Stull paper and in unusual cold-dry combinations.
• The calculator does not directly account for site elevation, barometric pressure variation, radiation, or clothing.
• For critical occupational or medical safety decisions, measured wet-bulb or WBGT instruments are stronger evidence than an estimate.

Use this tool for interpretation and screening. If the decision is about exposure limits in sun or work-rest guidance, compare the result with the WBGT calculator and local protocols.

Sources & references

• NOAA National Weather Service - Dew point glossary
• NOAA National Weather Service - Relative humidity glossary
• NOAA National Weather Service - Dry bulb, wet bulb, and dew point definitions
• NOAA National Weather Service - Vapor pressure glossary
• American Meteorological Society - Stull wet-bulb approximation
• NIST Chemistry WebBook - Water data
• Schema.org - FAQPage and WebApplication vocabulary