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Dew Point Calculator — °C/°F, RH & Reverse Solve

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Solve for Choose the unknown. The two required known values appear below.Temperature unit Temperature values share this display/input unit; the Magnus relationship is evaluated in °C internally.Air temperature Measured dry-bulb air temperature.Relative humidity (%) Enter a value greater than 0% and no more than 100%.

Calculated result

16.7 °C dew point

Air temperature: 25 °C (77 °F)

Dew point: 16.7 °C (62.1 °F)

Relative humidity: 60%

Dew-point depression: 8.3 °C (14.94 °F)

Saturation vapor pressure at air temperature: 31.62 hPa

Actual vapor pressure: 18.97 hPa

Dew-point sensitivity at 25 °C air temperature

RH	Dew point °C	Dew point °F	Depression °C
30%	6.2	43.2	18.8
50%	13.9	56.9	11.1
70%	19.1	66.5	5.9
90%	23.2	73.8	1.8

Show the working

1. Convert air temperature to the Magnus working unit: 25 °C = 25 °C.
2. γ = 17.625 × 25 / (243.04 + 25) + ln(60/100) = 1.133052.
3. Td = 243.04 × 1.133052 / (17.625 − 1.133052) = 16.698 °C.

Magnus is an approximation. Below freezing, dew point over liquid water and frost point over ice are different quantities; use an ice-aware psychrometric method when frost-point accuracy matters.

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