Dew point calculator
Dew Point Calculator — Air Moisture & Condensation Estimator
The Dew Point Calculator allows you to determine the exact temperature at which air becomes saturated with water vapor — the point when dew, fog, or condensation starts to form. This tool is essential for HVAC design, weather forecasting, environmental control, and comfort analysis.
How Dew point calculator Works
The dew point represents the temperature at which relative humidity reaches 100%. Below this temperature, moisture begins to condense on surfaces or in the air. A high dew point indicates high moisture content — and greater discomfort in warm environments.
Formula Used (Magnus–Tetens Equation)
The calculator applies the standard Magnus–Tetens approximation for the dew point:
α = ln(RH / 100) + (a × T) / (b + T) Dew Point (°C) = (b × α) / (a − α)
- T — air temperature (°C)
- RH — relative humidity (%)
- a = 17.62, b = 243.12 — constants valid for water vapor over liquid water
Example Calculation
For example, if the air temperature is 20 °C and the relative humidity is 65%, the dew point temperature is approximately 13.2 °C. If air cools below this temperature, condensation or fog will form.
Applications
- Predicting condensation on windows, walls, or HVAC coils
- Comfort level analysis in weather and climate studies
- Industrial drying, storage, and environmental control
- Forecasting fog, dew, and humidity conditions
Interpretation Guide
| Dew Point (°C) | Comfort Level |
|---|---|
| < 10 | Dry and comfortable |
| 10 – 15 | Pleasant |
| 16 – 20 | Humid but tolerable |
| > 20 | Very humid and uncomfortable |
FAQ
What is the dew point used for?
The dew point helps identify when moisture will condense — critical in HVAC design, agriculture, and weather prediction.
Is dew point the same as humidity?
No — humidity measures how saturated the air is, while dew point expresses the actual temperature at which saturation occurs.
Does the calculator support Fahrenheit?
Yes, you can switch between Celsius and Fahrenheit units instantly.
References
- Lawrence, M.G. (2005). The relationship between relative humidity and the dewpoint temperature in moist air. Bulletin of the American Meteorological Society, 86(2), 225–233.
- Wikipedia: Dew Point
- Magnus–Tetens Approximation Explained
