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Calcimator

Dew Point Calculator

Calculate the dew point temperature from air temperature and relative humidity. Includes comfort level assessment and frost risk.

Inputs

°
%

Results

Dew Point

67.2

Comfort LevelOppressive
Temp/Dewpoint Spread12.8°
Frost RiskNo
How to Use This Calculator
  1. Select your Temperature Unit (Fahrenheit or Celsius).
  2. Enter the Air Temperature.
  3. Set the Relative Humidity (%).
  4. Review the Dew Point temperature, Comfort Level, Temp/Dewpoint Spread, and Frost Risk indication.

How the result changes with Air Temperature

Air TemperatureDew Point
-23-30.9
199.2
7158.6
11398.3

What each input means

Temperature Unit
Measurement system to use.
Air Temperature
Temperature in the selected unit.
Relative Humidity
Relative humidity as a percentage.

How this is calculated

Formula

Uses the Magnus formula: Td = (b × α) / (a - α), where α = (a × T) / (b + T) + ln(RH/100). Constants: a = 17.27, b = 237.7°C.

Worked example, using the default values

  1. Identify Input Parameters
    Temperature Unit = 0, Air Temperature = 80, Relative Humidity = 65 = 3 input(s) provided
  2. Calculate Dew Point
    67.2 = 67.2
  3. Calculate Comfort Level
    Oppressive = Oppressive
  4. Calculate Temp/Dewpoint Spread
    Temp/Dewpoint Spread = round((displayTemp - displayDewPoint) * 10) / 10
    12.8 = 12.8

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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