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Dew Point & Humidity Calculator - Online Celsius Fahrenheit Tool

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Dew Point & Humidity Calculator

Calculate dew point, relative humidity, and absolute humidity — switch between Celsius & Fahrenheit instantly.

Calculate Dew Point
Calculate Relative Humidity
Temperature Unit
°C
Range: -40 to 60 °C
%
1% 50% 100%
Enter values & calculate
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Dry Comfortable Humid Oppressive
—
Absolute Humidity — g/m³
Vapor Pressure — hPa
What is Dew Point?

Dew point is the temperature at which air becomes saturated with moisture and water droplets begin to form. A higher dew point means more moisture in the air. Unlike relative humidity, dew point is an absolute measure of atmospheric moisture and directly relates to human comfort.

Comfort Scale
  • <10°C Very dry & comfortable
  • 10–16°C Comfortable
  • 16–21°C Slightly humid
  • 21–24°C Humid & sticky
  • >24°C Oppressive & muggy
Practical Uses
  • 🏠 Prevent window condensation & mold growth
  • 🌾 Monitor greenhouse & crop conditions
  • 🏊 Optimize indoor pool humidity
  • ❄️ Predict frost formation on surfaces
  • 🏗️ Concrete pouring & curing conditions
  • 🖼️ Museum & art preservation environments

Frequently Asked Questions

What is dew point temperature?

Dew point is the temperature to which air must be cooled for water vapor to condense into liquid water (dew). At the dew point, relative humidity reaches 100%. It's a direct measure of how much moisture is in the air — the higher the dew point, the more humid it feels.

Why is dew point better than relative humidity for comfort?

Relative humidity depends on temperature, so it changes throughout the day as temperatures rise and fall — even if the actual moisture content stays the same. Dew point is an absolute measure, making it a far better indicator of how humid it truly feels to the human body.

How is dew point calculated?

This tool uses the Magnus formula: γ(T,RH) = (a×T)/(b+T) + ln(RH/100), then Dew Point = (b×γ)/(a−γ), where a=17.27 and b=237.7 (for Celsius). It's accurate to within ±0.4°C for most atmospheric conditions. This is the industry-standard approximation used in meteorology.

At what dew point does mold grow?

Mold typically grows when relative humidity stays above 60-70% for extended periods, which often corresponds to a dew point above 13-15°C (55-59°F) in indoor environments. Keeping indoor dew point below 12°C (54°F) significantly reduces mold risk on cooler surfaces.

Can dew point be higher than air temperature?

No. Physically, dew point cannot exceed the air temperature because that would imply relative humidity greater than 100%, which is not possible under normal atmospheric conditions. If your calculation shows dew point > temperature, check your inputs — this indicates supersaturation.

How do I convert dew point between Celsius and Fahrenheit?

Use the standard formula: °F = °C × 9/5 + 32. For example, a dew point of 15°C equals 59°F. Our tool handles this conversion automatically — simply toggle the unit switch and all temperatures update instantly, including the dew point result.

What is absolute humidity and how is it different?

Absolute humidity measures the total mass of water vapor per cubic meter of air (g/m³). Unlike relative humidity (which is a percentage), absolute humidity tells you exactly how much water is in the air. Our tool calculates this automatically using vapor pressure and temperature.

What dew point feels comfortable for most people?

Most people feel comfortable with a dew point between 10°C and 16°C (50-60°F). Below 10°C feels dry (may cause dry skin/eyes), while above 21°C (70°F) feels oppressively humid and sticky. The ideal indoor dew point for comfort and health is around 12-14°C (54-57°F).

Calculations use the Magnus approximation (a=17.27, b=237.7 for °C). Accuracy: ±0.4°C for temperatures 0–60°C. Results are for informational purposes. For critical applications, consult professional meteorological instruments.
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