Dew Point Calculator

The Dew Point Calculator determines the dew point temperature from air temperature and relative humidity. The dew point is the temperature at which air becomes saturated and water vapor begins to condense, making it crucial for HVAC design, weather forecasting, and condensation prevention.

Modify the values and click the calculate button to use
Air Temperature °C
Relative Humidity %
Temperature Unit  
Atmospheric Pressure kPa

Related Relative Humidity Calculator | Wet Bulb Calculator | Absolute Humidity Calculator

Understanding Dew Point

The dew point is the temperature at which air becomes saturated with water vapor. When air is cooled to its dew point temperature, condensation begins to form on surfaces. This concept is fundamental to understanding humidity, weather patterns, and moisture control in buildings.

Key Concepts

Saturation

At the dew point temperature, the air holds the maximum amount of water vapor possible at that temperature and pressure. Any further cooling will result in condensation.

Relationship to Relative Humidity

The closer the air temperature is to the dew point, the higher the relative humidity. When air temperature equals dew point temperature, relative humidity is 100%.

Calculation Method

The dew point is calculated using the Magnus formula, which provides an accurate approximation for most practical applications:

Magnus Formula

α = ln(RH/100) + (a × T)/(b + T)

Td = (b × α)/(a - α)

Where:

  • T = Air temperature (°C)
  • RH = Relative humidity (%)
  • a = 17.27 (constant)
  • b = 237.7 (constant)
  • Td = Dew point temperature (°C)

Practical Applications

HVAC Systems

Building Science

Weather and Climate

Dew Point Comfort Levels

Dew Point (°C) Dew Point (°F) Comfort Level Description
< 10 < 50 Very Dry May feel dry, static electricity
10-13 50-55 Comfortable Pleasant for most people
13-16 55-60 Slightly Humid Noticeable but acceptable
16-18 60-65 Humid Somewhat uncomfortable
18-21 65-70 Very Humid Oppressive for most people
> 21 > 70 Extremely Humid Dangerous, heat stress risk

Factors Affecting Dew Point

Atmospheric Pressure

Geographic Location

Measurement and Monitoring

Direct Measurement

Calculated from Other Parameters

Design Considerations

Surface Temperature Control

Ventilation Strategies

Note: Dew point calculations assume standard atmospheric conditions. For precise applications, consider local atmospheric pressure and use calibrated instruments for critical measurements.