HumidCalc

Accurately calculates humidity and dew point using numerical analysis. Ideal for HVAC, building management, and agricultural applications.

＊Weather data supported＊ A versatile humidity calculation app for everyone from general users to engineers — also suitable for agricultural applications. This app allows you to easily calculate indicators such as the Discomfort Index, WBGT (estimated heat stress index), Volumetric Absolute Humidity (an important indicator for influenza prevention), and Humidity Deficit (HD) used in agriculture, using weather data. You can also calculate a wide range of air properties from dry-bulb temperature (normal air temperature) and wet-bulb temperature obtained from ventilated psychrometers such as the Assmann psychrometer. Atmospheric pressure can be entered manually. The app supports 11 indicators across 15 calculation items, and unit conversion between Celsius/Fahrenheit and SI/Imperial units can be performed instantly by switching the temperature unit setting.

■ High-Precision Calculation Engine This app uses the Wexler–Hyland equations combined with numerical analysis, enabling highly accurate and stable calculations across a wide range of environmental conditions.

■Newly Added Features In the latest version, the app now supports:

• Frost point temperature
• Vapor Pressure Deficit (VPD) These additions make the app even more useful for cold environments, agriculture, and environmental control applications.

■ Calculable Indicators

• Dew Point Temperature
  • Frost point temperature
• Relative Humidity
• Humidity Ratio(Absolute Humidity)
  • Mass-based absolute humidity
  • High-resolution mass-based absolute humidity
  • Volumetric absolute humidity
• Humidity Deficit (HD)
  • Vapor Pressure Deficit (VPD)
• Enthalpy
• Specific Volume
• Saturation Vapor Pressure
• Water Vapor Partial Pressure
• Boiling Point of Water
• WBGT (Estimated value)
• Discomfort Index (DI) The Discomfort Index (DI) is calculated as: DI = 0.4 × (Td + Tw) + 15 (°F). [Td: Dry Bulb, Tw: Wet Bulb]

■ Weather Data & Sensors By tapping the Weather button, you can obtain the current atmospheric pressure, dry-bulb temperature, and wet-bulb temperature. On devices equipped with a barometric pressure sensor (such as iPhone 6 and later), pressing the MEAS button allows pressure measurement directly from the sensor. The wet-bulb condition can be set to either Normal or Frozen. (The Frozen option becomes effective when the wet-bulb temperature is below the freezing point.) Even when using non-ventilated psychrometers such as the August psychrometer, the app can display corrected indicators with a single button press. (For accuracy reasons, ventilated psychrometers are recommended.)

■App Ecosystem Integration You can directly receive calculated dry-bulb and wet-bulb temperatures from the companion app “Calculator of Air”. (Please note that calculations must be performed in Calculator of Air before data can be transferred.) By combining HumidCalc with Calculator of Air, you can, for example, derive multiple air properties from known dry-bulb temperature and relative humidity values.

■Input Ranges

• Dry-bulb & wet-bulb temperature: −30°C to 50°C (−22°F to 122°F)
• Atmospheric pressure: 600 hPa to 2475 hPa (17.72 inHg to 73.09 inHg)

■Data Source This app uses OpenWeatherMap data (CC BY-SA 4.0).

■Notes When using an August psychrometer, calculations assume an air velocity at the sensing element of 0.5 m/s or less. As a result, calculated values may differ from those listed in humidity tables included with commercial August psychrometers.

■Disclaimer

1. 1. Please use values within reasonable temperature ranges (approximately 0°C to 40°C / 32°F to 104°F). Extremely unusual inputs may produce inaccurate results.
2. While every effort has been made to ensure high precision, minor errors may occur due to floating-point limitations.
3. The developer assumes no responsibility for any damages resulting from the use of this app.