What dew point means
Dew point is the temperature where air becomes saturated with moisture. At that point, dew, fog, or condensation can form under the right conditions.
Dew Point Calculator
Calculate the dew point temperature from air temperature and humidity.
Weather inputs
Enter air temperature and relative humidity. The calculator uses a common dew point approximation.
percent
Dew point temperature
16.7 °C
16.7 °C, 62.0 °F
Comfort category
Slightly humid
Dew point spread
8.3 °C
Humidity feel
Humidity may be noticeable, especially during warm weather or low airflow.
Condensation risk
Lower condensation risk
Relative humidity used
60%
Formula used
Magnus approximation
Copy result
Copy dew point, comfort category, dew point spread, humidity, and formula note.
Formula approximation
The result uses the Magnus approximation for typical weather and indoor comfort ranges.
Comfort interpretation
Comfort varies by person, activity, clothing, wind, shade, and indoor airflow.
Condensation note
Condensation depends on surface temperature, airflow, insulation, and local conditions.
Weather safety
Use official forecasts and alerts for severe heat, storms, fog, or hazardous weather.
Local calculation
Inputs are processed in your browser. No external weather API is required.
Dynamic weather and comfort insights
Comfort reading
Humidity may be noticeable, especially during warm weather or low airflow.
Condensation check
The air temperature is comfortably above the dew point.
Context note
For outdoor use, dew point can help explain fog, dew, humidity comfort, and changing weather feel.
Dew point comfort breakdown
Dew point value
16.7 °C
Comfort category
Slightly humid
Humidity feel
Humidity may be noticeable, especially during warm weather or low airflow.
Condensation or fog potential
Lower condensation risk
Inputs used
25 °C, 60% RH
Temperature minus dew point
8.3 °C
Dew point comfort guide
Below 50 °F or 10 °C
Dry or comfortable
Air usually feels dry or mild for many people
50 to 60 °F or 10 to 16 °C
Comfortable
Often pleasant for outdoor and indoor comfort
60 to 65 °F or 16 to 18 °C
Slightly humid
Humidity becomes more noticeable
65 to 70 °F or 18 to 21 °C
Humid
Can feel sticky during warm weather
Above 70 °F or 21 °C
Very humid
Often uncomfortable for many people
Condensation guide
Temperature far above dew point
Lower risk
Air has more room before saturation
Temperature near dew point
Higher risk
Fog, dew, or surface moisture may become more likely
Temperature at or below dew point
Condensation likely
Surface moisture can form if surfaces are cool enough
Indoor humidity reference
Dry indoor air
Low dew point
May feel dry, especially in heated rooms
Comfortable indoor range
Moderate dew point
Often comfortable when airflow and temperature are stable
High humidity risk
High dew point
Can increase condensation risk on cool windows and walls
Dew point guide
These notes explain dew point concepts without repeating the calculator result.
Dew point vs relative humidity
Relative humidity depends on temperature. Dew point gives a more direct sense of how much moisture is actually in the air.
Why dew point affects comfort
Higher dew points make sweat evaporate more slowly, which can make warm conditions feel stickier or more uncomfortable.
How dew point relates to condensation
Condensation may form when a surface is at or below the dew point, especially on cool windows, pipes, walls, or outdoor surfaces.
Using dew point for indoor comfort
Indoor dew point can help explain window condensation, musty conditions, and how humid a room may feel.
Limitations of dew point calculations
The formula is approximate, sensor accuracy matters, and local conditions can affect comfort and condensation risk.
Formula
γ = ln(RH / 100) + (a × T) / (b + T)
Dew Point = (b × γ) / (a − γ)
Variables
- T is air temperature in Celsius.
- RH is relative humidity as a percentage.
- a and b are approximation constants.
- Common constants are a = 17.27 and b = 237.7 °C.
Worked example
At 25 °C and 60% relative humidity, the Magnus approximation gives a dew point near 16.7 °C, which is about 62.1 °F.
Assumptions
The formula works best for typical weather and indoor comfort ranges with reliable temperature and humidity inputs.
Limitations
Dew point estimates are approximate. Weather safety decisions should use official local forecasts and alerts.
Frequently asked questions
What does dew point mean?
Dew point is the temperature where air becomes saturated with water vapor. When air cools to that point, condensation can begin on suitable surfaces.
Is dew point more useful than relative humidity?
Dew point is often easier for comfort because it reflects the actual moisture in the air. Relative humidity changes with temperature, even when moisture content stays similar.
What dew point feels humid?
Many people start to notice humidity around 60 °F or 16 °C. Dew points above 70 °F or 21 °C often feel very humid for many people.
Can dew point predict condensation?
It can help estimate condensation risk. Condensation is more likely when a surface temperature is at or below the dew point.
Why does dew point change with humidity?
Higher relative humidity usually means the air is closer to saturation, so the dew point moves closer to the air temperature.
Can I use this calculator for indoor humidity?
Yes. Indoor dew point can help understand condensation risk on windows, walls, pipes, and other cool surfaces.
How accurate is a dew point calculator?
This calculator uses the Magnus approximation, which is useful for typical weather and indoor comfort ranges. Sensor accuracy affects the final result.
What is the difference between dew point and heat index?
Dew point measures moisture in the air. Heat index estimates how hot conditions feel by combining temperature and humidity.
Does pressure affect dew point?
Pressure can matter in advanced meteorology, but temperature and relative humidity are enough for common comfort and condensation estimates.
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