Calculate Comfort5.7 - App Store

Calculate Comfort computes the psychrometric properties of moist air - dew point, wet bulb temperature, absolute humidity, enthalpy and more - from temperature and humidity. Turn a dial instead of reading a psychrometric chart. Built for HVAC design, instrumentation, building maintenance and condensation control.

Units: the Pro version switches the entire readout between IP and SI in one tap, °F⇄°C included. Useful when your measurements are in IP but the equipment data is in SI. If you work only in Fahrenheit, our companion app Psychrometer °F opens in Fahrenheit by default.

■ Who it's for
・HVAC engineers and contractors who need moist-air properties on site
・Technicians converting psychrometer readings to relative humidity
・Anyone assessing condensation or mold risk from dew point
・Students learning to read a psychrometric chart

■ What it calculates
Enter temperature plus relative humidity, dew point or wet bulb temperature:
・Relative humidity (%RH)
・Dew point (°C DP) / frost point (°C FP), switchable below 0 °C
・Wet-bulb temperature (°C WB)
・Mixing ratio, gravimetric absolute humidity (g/kg)
・Absolute humidity, volumetric (g/m³)
・Enthalpy (kJ/kg), for load calculations
・Specific volume (m³/kg)
・Vapor pressure and saturated vapor pressure (hPa)
・Discomfort index (DI)
・Estimated WBGT heat index (indoor, no solar load)
・Comfort indicator (18-28 °C, 40-70 % RH)

■ Main features
◯ Three input modes: relative humidity, dew point or wet bulb temperature. Tap the % icon to switch; keyboard entry also available.
◯ Works in place of a psychrometric chart. Dew point mode traces constant absolute humidity - sensible heating and cooling. Wet bulb mode traces the constant wet-bulb line - humidification and dehumidification.
◯ Three psychrometer types: aspirated (Assmann), wall-mounted (August) and sling. Below freezing you can set whether the wet bulb is iced; below -10 °C this applies automatically, except for the sling type.
◯ Pressure-corrected calculation: standard pressure (1013.25 hPa), built-in barometer, weather data or manual entry (800-1200 hPa).
◯ Automatic weather retrieval from your location, with a recommended indoor temperature (ASHRAE Standard 55). Choose OpenWeatherMap or Apple Weather.
◯ Works offline. A connection and location permission are needed only to fetch outdoor weather.
◯ Comfort indicator in color and emoji.

[Common gestures]
・Pressure and index readouts: tap to open settings
・Outdoor air (weather icon), dew point input, wet bulb input and reset buttons: touch and hold to open settings

■ Pro version (one-time in-app purchase)
・Removes all ads
・IP ⇄ SI unit switching in one tap: °C⇄°F, g/kg⇄gr/lb, g/m³⇄gr/ft³, kJ/kg⇄BTU/lb, m³/kg⇄ft³/lb, hPa⇄inHg
・Text export of calculation results
・Extended pressure input: 23-36 inHg
・Selectable saturation vapor pressure formula: Sonntag (WMO), Hyland-Wexler (ASHRAE), Wagner-Pruß (IAPWS-95), Goff-Gratch, Magnus-Tetens

■ Supported devices
iPhone with iOS 16.0 or later. Also runs on Apple M1 Mac (macOS 13.0 or later) and visionOS 1.0. Home Screen: ComfortCalc. App header: Psychrometer°Calc.

■ What it does not do
・Does not measure temperature or humidity with the device; outdoor values come from weather data
・Does not perform measured WBGT with a globe thermometer
・Does not draw a psychrometric chart

■ Calculation basis
・Saturated vapor pressure: Sonntag; other formulas in Pro
・Vapor pressure: JIS Z 8806
・Relative humidity and dew point: JIS and WMO; denominator over supercooled water
・Enthalpy: ASHRAE definition
・Recommended indoor temperature: ASHRAE Standard 55

■ Notes
Extreme input values increase error and may produce an error state. Rounding may shift the last digit when switching modes. Correctness of results is not guaranteed and no liability is accepted for damages arising from use.

Documentation, FAQ and calculation specs:
https://www7b.biglobe.ne.jp/~kanayama/PsychrometerCalc/

Version History • Added a link to the support page.
• Improved the main screen layout for the paid Pro version. 5.7 Aug 27 - Fixed an issue where comments in the Comfort Popup were not displayed correctly.
- Other minor improvements. 5.6 Jul 26 • Fixed a bug that switched the app into test mode while acquiring outdoor air (temperature). Other minor bugs were also fixed.
• When the atmospheric pressure mode is set to [Sensor] or [Weather], tapping the [Outdoor Air] button now retrieves it automatically.
• You can now choose the saturation vapour pressure formula. (Pro)
Sonntag (WMO) / Hyland-Wexler (ASHRAE) / Wagner-Pruss (IAPWS-95) / Goff-Gratch (classical) / Tetens (WMO approximation)
In normal use the results differ very little. These formulas were built in for verification during development and are now available. 5.5 Jul 2 ・Added a Comfort Screen.
You can now view the recommended indoor temperature based on the current outdoor temperature and humidity. (ASHRAE Standard 55)
You can also check the suggested heating and cooling target temperatures, quick tips on ventilation, dehumidification, humidification, mold prevention, and dryness, as well as alerts for heat and sudden temperature changes — all in one place.
・You can now choose a wallpaper. Select from Silver, Gold, Copper, Stone, Wood, or Glass. 5.4 Jun 12 Added automatic switching for the WBGT heat stress index.
Fixed issues with text export in the Pro version and added multilingual support.
Improved the UI. 5.3 May 13 Fixed display issues on the atmospheric pressure adjustment screen.
Improved behavior so that specific volume updates correctly when atmospheric pressure is changed.
Fixed an issue where the frost point temperature display did not switch correctly under sub-freezing conditions.
Revised the enthalpy calculation formula to comply with the ASHRAE definition.Enthalpy: ASHRAE 5.2 Feb 10 Fixed an issue that allowed out-of-range values on the atmospheric pressure input screen.
Adjusted font sizes to improve readability.
Optimized the keyboard.
Added multilingual support. 5.1 12/23/2025 You can now long-press the Outdoor Air button to select and switch between weather data sources (OpenWeatherMap / AppleWeather).
Added support for displaying WBGT (Wet Bulb Globe Temperature). Tapping the DI item now opens a screen to switch between the Discomfort Index (DI) and WBGT.
Tapping the atmospheric pressure in the upper right now opens the atmospheric pressure input screen.
When in Dew Point Temperature input mode, long-pressing the input switch button now opens a screen to switch between dew point and frost point calculations when below freezing.
When in Wet Bulb Temperature input mode, long-pressing the input switch button now opens a screen to select the type of psychrometer (Assmann, August, or Sling). 5.0 08/20/2025 Support for access to barometric pressure sensors, improved input dialing, and Ukrainian language support. 4.2 12/02/2024 AppTrackingTransparency compatible
Change of comfort display
Accuracy improvement of absolute humidity calculation 4.1 03/01/2022 Improved user interface. Addition of Pro Version. 4.0 04/21/2021 Added psychrometer type.
If you use a psychrometer, please choose from 3 types.
(When not using, please use it as it is as a Assmann.)
Asssmann ... Aspirator psychrometer. It is a forced ventilation type.
Simple ... August psychrometer.Old type without forced ventilation.Wall-mounted.
Sling ... Sling Psychrometer.Type that swings around by hand.
(If you press the reset button or the outside air button, it will return to the ventilation type. With the exception of the ventilation type, only wet bulb input is possible.)

Changed the dew point(°CDP) temperature display below freezing to the frost point(°CFP) temperature display. 3.5 06/10/2020 Dark mode support.
Bug fix of dew point temperature input below freezing point.
Improve back calculation accuracy of wet-bulb temperature.
Other display bug fixes. 3.4 01/23/2020 Temperature and humidity standards now be displayed.
When the temperature falls between 17 ° C~28 ° C. relative humidity of 40%~70%
A good mark will be displayed. 3.3 06/04/2018 It corresponds to iOS 11. It corresponds to iPhoneX.
Dial input is now more convenient.
Fixed bug relative humidity and dew point temperature in below freezing.
Switching display of icing and overcooling status in wet bulb input mode.
Calculation of over-saturated air. (Humidity can be calculated over 100%.)
Localized in German, Russian, Italian, French,Indonesian,Thai 3.2 03/23/2018 Display comfort in color.Add reset button. The value can be set.
Fixed minor bugs, such as when not recalculated by dialing. 3.1 06/28/2017 Equipped with input Dial. The value input became smooth and intuitive.
Added input mode. Added relative humidity input mode and dew point temperature input mode.input mode.
As usual, you can also calculate in wet bulb input mode.
Added open air input. You can automatically enter outside temperature and humidity from the weather information.(Please allow use of location information.)
Add absolute humidity conversion. Displays the weight absolute humidity and volume absolute humidity by switching.
Addition of saturated vapor pressure indication. The calculation formula uses exact SONNTAG expression.
In addition, we have added some minor improvements.
higher versions like iOS 10 3.0 03/16/2017 iOS9 support
Upgrade planned.Coming soon. 2.8 01/14/2016 Add clear button(AC) and the tag button (＜＞).
You can now be quickly calculated. 2.7 06/10/2015 Temperature–humidity index (Discomfort index) added 2.6 05/04/2015 Add Information view
Adjustment etc 2.5 01/09/2015 Supports for the barometric pressure sensor. iPhone6,iPhone 6 Plus 2.4 11/04/2014 change to custom keypad 2.3 02/04/2014 Minor bug fixes 2.2.1 12/01/2013 The minus display fix in 0 degrees of dew point 2.2 11/27/2013