Calculadora de Ponto de Orvalho
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
Td = 243,12·γ/(17,62−γ); γ = ln(UR/100)+17,62T/(243,12+T)
About this calculator
The dew point calculator determines the temperature at which air becomes saturated with moisture, initiating condensation. It uses the Magnus formula, which relates air temperature (T) and relative humidity (RH). First, the parameter γ = ln(RH/100) + 17.62·T/(243.12+T) is calculated. Then, the dew point is given by Td = 243.12·γ/(17.62−γ).
This tool is useful for predicting dew, frost, or fog formation, especially in outdoor activities such as agriculture, aviation, and construction. For example, farmers use it to decide on irrigation or crop protection against frost. Pilots check the dew point to assess the risk of ice formation on wings.
Important precautions: the Magnus formula is accurate for temperatures between -40°C and 50°C and relative humidity between 0% and 100%. Outside these ranges, results may be inaccurate. Additionally, the calculated dew point assumes constant atmospheric pressure; significant altitude variations can affect the actual value.
Understanding the dew point helps avoid problems such as condensation on electronic equipment, fogging of windows, and moisture damage to sensitive materials. Use this calculator to plan activities or protect your assets.
Frequently asked questions
What is dew point?
It is the temperature at which water vapor in the air begins to condense, forming dew, frost, or fog.
How does relative humidity affect dew point?
The higher the relative humidity, the closer the dew point is to the air temperature. At 100% RH, they are equal.
Can I use this calculator for high altitudes?
The Magnus formula is most accurate at sea level. At high altitudes, lower atmospheric pressure may cause slight deviations.
How accurate is the Magnus formula?
It is accurate for temperatures between -40°C and 50°C and relative humidity between 0% and 100%, with typical error below 0.5°C.
Why is dew point important in aviation?
It helps predict ice formation on wings and reduced visibility due to fog, both critical for flight safety.