Engineering Tools
Dew Point Calculator
Enter dry-bulb temperature and relative humidity to instantly calculate dew point temperature, absolute humidity, and mixing ratio. Suitable for HVAC engineering design, condensation prevention analysis, and dehumidification system planning.
Dew Point Temperature Calculation
Calculation Results
Calculation Formula (Magnus Formula)
This tool uses the Magnus approximation formula to calculate dew point temperature. It is applicable for the typical temperature and humidity ranges encountered in HVAC engineering (0°C to 60°C, RH 1% to 100%).
Dew Point Temperature Calculation:
a = 17.27, b = 237.7
γ = (a × T) / (b + T) + ln(RH / 100)
Td = (b × γ) / (a − γ)
Saturation Vapor Pressure:
es = 6.112 × exp((17.67 × T) / (T + 243.5)) (unit: hPa)
Actual Vapor Pressure:
e = es × (RH / 100)
Absolute Humidity:
AH = 217 × e / (T + 273.15) (unit: g/m³)
Mixing Ratio (Humidity Ratio):
w = 622 × e / (1013.25 − e) (unit: g/kg dry air)
Where T is the dry-bulb temperature (°C), RH is the relative humidity (%), and 1013.25 hPa is the standard atmospheric pressure. The Magnus formula has an estimation error of less than ±0.4°C within common temperature ranges, providing sufficient accuracy for most HVAC engineering applications.
Frequently Asked Questions
What is the dew point temperature?
The dew point temperature is the temperature at which water vapor in the air begins to condense into dew. When a surface temperature falls below the dew point, condensation occurs. In HVAC engineering, it is commonly used to assess insulation requirements for piping.
What is the relationship between dew point and condensation?
When the surface temperature of refrigerant piping or ductwork falls below the dew point temperature of the surrounding air, condensation forms on the surface. HVAC system design must ensure that insulation thickness is sufficient to keep the outer surface temperature above the dew point.
What is the difference between relative humidity and absolute humidity?
Relative humidity is the ratio of actual water vapor to saturated water vapor at the same temperature (%), and varies with temperature. Absolute humidity (g/kg) is the mass of water vapor per kilogram of dry air, independent of temperature.
Professional Consultation
Need Professional HVAC Engineering?
Online tools provide preliminary estimates for reference. Actual engineering design requires consideration of many additional professional factors. Contact our engineering team for precise HVAC system planning.