Dry Bulb Wet Bulb Calculator
The Dry Bulb Wet Bulb Calculator estimates relative humidity and dew point based on temperature and pressure readings. This tool helps HVAC technicians and engineers optimize system performance and air quality. Whether you are designing a ventilation system, troubleshooting an AC unit, or monitoring greenhouse conditions, this calculator provides precise psychrometric data for better decision-making.
How Relative Humidity and Dew Point Are Calculated
Relative humidity measures the current water vapor in the air compared to the maximum it can hold. The dew point is the temperature where air becomes completely saturated and moisture begins to condense. This tool uses the Tetens equation to find the saturation pressure at both temperature points.
RH = 100 × (Pws(Twb) - P × (Tdb - Twb) × 0.00066) / Pws(Tdb)
Where:
- RH = Relative Humidity
- Pws = Saturation vapor pressure
- Tdb = Dry bulb temperature
- Twb = Wet bulb temperature
- P = Atmospheric pressure
First, the calculator determines the saturation vapor pressure for both the dry and wet bulb temperatures. Then, it applies the psychrometric relationship to find the actual vapor pressure in the air. Finally, it uses the Magnus formula approximation to calculate the dew point temperature based on the resulting relative humidity. This scientific approach ensures high accuracy for engineering tasks.
What Your Relative Humidity and Dew Point Mean
These numbers reveal how much moisture is in the air and how that affects the environment. Understanding these values helps you control humidity levels for health, comfort, and equipment efficiency.
HVAC System Sizing: If the relative humidity is above 60% and the dew point exceeds 20°C (68°F), your cooling equipment works harder to remove moisture. You may need a larger capacity dehumidifier or AC unit to handle the latent heat load effectively.
Indoor Comfort: For human comfort and health, aim for a relative humidity between 40% and 50%. Readings below 30% can cause dry skin and respiratory irritation, while readings above 60% create a muggy feeling and promote mold growth on surfaces.
Industrial Processes: In manufacturing or storage, maintaining a specific dew point prevents condensation on machinery and products. A stable dew point ensures that materials like wood or paper do not warp due to moisture absorption.
Important: Remember that atmospheric pressure changes with altitude. Always adjust the pressure input if you are working at elevations significantly different from sea level to ensure accuracy.
This calculator provides estimates based on standard psychrometric formulas. For critical engineering, medical, or industrial applications, professional measurement equipment and consultation with certified experts are recommended. Results may vary slightly from actual conditions due to sensor accuracy and local environmental factors.
Monitor these values regularly to spot trends and adjust your climate control systems before moisture problems arise.