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`DP = (B_1*(ln(( RH )/100) + (A_1* t )/(B_1 + t )))/(A_1 -ln(( RH )/100)-A_1* t /(B_1+ t ))`

Enter a value for all fields

The **Dew Point Temperature** calculator computes the dew point (DP) based on the relative humidity (RH) and ambient temperature (t).

**INSTRUCTIONS:** Choose units and enter the following:

- (
**t**) Ambient Temperature - (
**RH**) Percent Relative Humidity

**Dew Point Temperature (DP):** The calculator returns the dew point temperature in degrees Celsius (C). However, this can be automatically converted to other temperature units via the pull-down menu.

This Dew Point Temperature equation computes the **Dew Point Temperature** given the Relative Humidity and ambient temperature. The Dew Point Temperature is the temperature air needs to cool to cause the water vapor already in the air to condense out as dew on surfaces. While there are many ways in which to estimate the Dew Point Temperature, Lawrence (2005) derived this formula based on the empirical formula by Magnus (1844) along with a definition of Relative Humidity. Constants A_{1} and B_{1} used in this equation were determined by Alduchov and Eskridge (1996). There are two different definitions of Relative Humidity. This formula assumes Relative Humidity is defined as the ratio of water vapor pressure (e) to the equilibrium vapor pressure over a plane of water ("saturation" vapor pressure (e_{s})) converted to a percent. If the alternative definition of Relative Humidity based on the water vapor mixing ratio is used, then this equation may report a slight error of up to ~3% of the dew point depression.

The Dew Point Temperature from percent relative humidity formula is:

DP (^{o}C) =(B_{1}*(ln(RH/100) + (A_{1}*t)/(B_{1} +t)))/(A_{1}-ln(RH/100)-A_{1}*t/(B_{1}+t))

where

- DP is the dew point temperature
- t is the ambient temperature °C
- RH is the Relative Humidity
- A
_{1}is a constant equal to 17.625 - B
_{1}is a constant equal to 243.04 °C

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Lawrence, M. G. (2005). The relationship between relative humidity and the dewpoint temperature in moist air: A simple conversion and applications. *Bulletin of the American Meteorological Society*, *86*(2), 225-233.

Magnus, G. (1844). Versuche über die Spannkräfte des Wasserdampfs. *Annalen der Physik*, *137*(2), 225-247.

Alduchov, O. A., & Eskridge, R. E. (1996). Improved Magnus form approximation of saturation vapor pressure. *Journal of Applied Meteorology*, *35*(4), 601-609.