Dew Point and Relative Humidity Calculator

Dew Point Formula:

\[ T_d = \frac{b \times \gamma}{a - \gamma} \] \[ \gamma = \ln\left(\frac{RH}{100}\right) + \frac{a \times T}{b + T} \]

Temperature (T):

°C

Relative Humidity (RH):

Constant (a):

Constant (b):

Dew Point Temperature (T_d):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is a Dew Point and Relative Humidity Calculator?

Definition: This calculator estimates the dew point temperature based on air temperature and relative humidity using the Magnus formula.

Purpose: It helps meteorologists, HVAC professionals, and weather enthusiasts determine when condensation will occur.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ T_d = \frac{b \times \gamma}{a - \gamma} \] \[ \gamma = \ln\left(\frac{RH}{100}\right) + \frac{a \times T}{b + T} \]

Where:

\( T_d \) — Dew point temperature (°C)
\( T \) — Air temperature (°C)
\( RH \) — Relative humidity (%)
\( a \) — Constant (typically 17.27)
\( b \) — Constant (typically 237.7)

Explanation: The formula approximates the relationship between temperature, humidity, and dew point using empirically derived constants.

3. Importance of Dew Point Calculation

Details: Knowing the dew point helps predict fog, frost, and condensation. It's critical for HVAC systems, agriculture, and industrial processes.

4. Using the Calculator

Tips: Enter the air temperature (°C), relative humidity (0-100%), and constants a and b (default values provided). All values must be valid.

5. Frequently Asked Questions (FAQ)

Q1: What is dew point temperature?
A: The temperature at which air becomes saturated with water vapor, causing condensation to form.

Q2: Why are constants a and b needed?
A: These are empirically derived values that make the Magnus formula accurate for typical atmospheric conditions.

Q3: When would I change the constants?
A: For extreme temperatures or special applications, different constants might be used (e.g., a=17.62, b=243.12 for some models).

Q4: What happens when RH is 100%?
A: The dew point equals the air temperature, meaning condensation is already occurring.

Q5: How accurate is this calculation?
A: The Magnus formula is accurate to within about ±0.4°C for temperatures between 0°C and 50°C.