Science & Lab Tools
Dew Point Calculator
Calculate the temperature at which water vapor in the air begins to condense
Enter temperature and humidity values to calculate the dew point
Related to Dew Point Calculator
The dew point calculator uses the Magnus formula, a widely accepted approximation in atmospheric sciences, to determine the temperature at which water vapor in the air begins to condense. This calculation takes into account both the current air temperature and relative humidity to predict when dew formation will occur.
The Magnus Formula
The calculator employs the Magnus-Tetens approximation, where the dew point (Td) is calculated using the formula: Td = (b × γ) / (a - γ) where γ = ln(RH/100) + (a × T)/(b + T) with constants a = 17.27 and b = 237.7°C for temperatures above 0°C
Variables Used
T = Air temperature in degrees Celsius
RH = Relative humidity in percentage
Td = Dew point temperature in degrees Celsius
The dew point temperature indicates when condensation will occur in the current atmospheric conditions. This value is crucial for understanding atmospheric moisture content and predicting various weather phenomena.
Dew Point Interpretation
• High dew point (>20°C): Indicates high humidity and potential discomfort
• Moderate dew point (10-20°C): Comfortable conditions
• Low dew point (<10°C): Indicates dry air conditions
• When air temperature reaches the dew point: Condensation occurs (100% relative humidity)
Practical Applications
• Weather forecasting and prediction of fog formation
• HVAC system design and operation
• Greenhouse climate control
• Industrial process control where moisture is critical
1. What exactly is the dew point?
The dew point is the temperature at which water vapor in the air begins to condense into liquid water at constant atmospheric pressure. It's a critical measure of atmospheric moisture content and helps predict when dew, fog, or frost might form.
2. Why is the dew point important?
The dew point is crucial for weather forecasting, comfort assessment, and industrial processes. It helps predict fog formation, indicates humidity levels, and is essential for controlling indoor climate conditions in buildings and greenhouses.
3. Can the dew point be higher than the air temperature?
No, the dew point temperature cannot be higher than the air temperature. When the air temperature equals the dew point, the relative humidity is 100%, and condensation occurs. This is why dew typically forms in the early morning when the air temperature drops to the dew point.
4. How does altitude affect dew point?
While the dew point calculation itself doesn't change with altitude, the atmospheric pressure does affect when condensation occurs. At higher altitudes, the lower atmospheric pressure means water vapor condenses at slightly different temperatures than at sea level.
5. What is the scientific source for this calculator?
This calculator implements the Magnus-Tetens formula, a widely accepted approximation in meteorology and atmospheric sciences. The formula was developed by Magnus (1844) and later refined by Tetens (1930). The specific constants used (a=17.27 and b=237.7°C) are based on the work published in the Bulletin of the American Meteorological Society (1980) and are recommended by the World Meteorological Organization (WMO) for temperatures above 0°C. The formula provides accuracy within ±0.4°C for temperatures between -45°C and +60°C at standard atmospheric pressure.