Humidity Converter
Convert between relative humidity, absolute humidity, specific humidity, dew point, and vapor pressure.
Definition: Absolute humidity is the mass of water vapour per unit volume of air, expressed in g/m³. Relative humidity is the ratio of the actual vapour pressure to the saturation vapour pressure at the same temperature, expressed as a percentage.
Relative Humidity Calculator
Humidity Level Reference
Comfort Level
Current Status
About Humidity
- Relative Humidity: Moisture in air vs maximum capacity
- Dew Point: Temperature where air becomes saturated
- Ideal Indoor: 30% - 50% relative humidity
How to Use the Humidity Calculator
Enter Temp
Input the current temperature in Celsius
Enter Humidity
Input relative humidity percentage (0-100%)
View Dew Point
See calculated dew point temperature
Check Comfort
Use reference guide for comfort levels
Understanding Humidity & Dew Point
What is Dew Point?
Dew point is the temperature at which air becomes saturated with water vapor, causing dew to form. It's a more accurate measure of atmospheric moisture comfort than relative humidity alone.
- • Relative Humidity: Percentage of moisture in air vs capacity
- • Dew Point: Temperature where condensation occurs
- • Comfort Index: How humidity affects human comfort
- • Health Impact: Effects on respiratory conditions
Why Monitor Humidity?
Proper humidity levels are crucial for health, comfort, and preserving property. Too dry causes irritation and damage; too humid promotes mold and discomfort.
- • Health: Ideal humidity (30-50%) prevents respiratory issues
- • Home Comfort: Prevent muggy or dry indoor conditions
- • Property Protection: Avoid mold or excessive dryness damage
- • Weather Planning: Understand outdoor comfort conditions
Instant Calculation
Real-time dew point calculation as you enter values.
100% Private
All calculations in your browser. No data stored or transmitted.
Completely Free
No registration or limits. Calculate humidity freely.
Humidity Conversion Formulas
Dew Point (Magnus Formula)
Td = (b · γ) / (a − γ)
Where T is air temperature in °C, RH is relative humidity in %, and a = 17.27 and b = 237.7 °C are Magnus coefficients. The formula is accurate to within about 0.35 °C for temperatures from −40 °C to +50 °C, which covers virtually all practical weather and indoor conditions.
Absolute Humidity
Absolute humidity is the mass of water vapor per volume of air. Here ea is the actual vapor pressure in hPa: ea = (RH / 100) × es, where es = 6.112 × exp(17.62 · T / (243.12 + T)) hPa is the saturation vapor pressure (Bolton 1980).
Specific Humidity & Vapor Pressure
Specific humidity is the ratio of water vapor mass to total moist air mass. P is atmospheric pressure (about 1013.25 hPa at sea level). Engineers and meteorologists prefer specific humidity because, unlike relative humidity, it does not change when air is heated or cooled at constant pressure.
Where Humidity Conversion Matters
HVAC & Building Management
Keeping indoor relative humidity between 40% and 60% prevents mold growth, protects wooden furniture, and reduces static electricity. Facility managers compare dew point against cold surface temperatures to predict condensation on windows, ducts, and pipes before it causes damage.
Weather & Meteorology
Dew point is the most direct measure of how humid the air feels. A dew point below 10 °C feels dry and crisp, 10–16 °C is comfortable, 16–20 °C noticeably humid, and above 20 °C feels muggy — above 24 °C is oppressive for most people. Forecasters track dew point to predict fog, frost, and thunderstorm potential.
Industry & Manufacturing
Painting, electronics assembly, pharmaceutical production, and food processing all specify strict humidity ranges. Too much moisture ruins powder coating and causes corrosion; too little causes brittle materials and static discharge that damages semiconductors. Absolute humidity in g/m³ is used to specify drying and storage conditions.
Agriculture & Storage
Grain spoils when stored above roughly 65% equilibrium relative humidity — monitoring dew point in silos prevents mold and mycotoxin growth. Greenhouse growers adjust vapor pressure deficit (VPD) to control transpiration: a VPD between 0.8 and 1.2 kPa is the sweet spot for most vegetables.
Frequently Asked Questions
What is the difference between relative humidity and absolute humidity?
Relative humidity (RH) expresses moisture as a percentage of the maximum amount of water vapor the air can hold at its current temperature, so it changes when temperature changes. Absolute humidity (AH) is the actual mass of water vapor per cubic meter of air (g/m³), and specific humidity is the mass of water vapor per kilogram of moist air (g/kg). At 25 °C and 50% RH, the absolute humidity is about 11.5 g/m³.
What dew point is considered comfortable?
A dew point below 10 °C feels dry, 10–16 °C feels comfortable, 16–20 °C is noticeably humid, and above 20 °C feels muggy. Dew point above 24 °C is oppressive for most people. Unlike relative humidity, dew point directly measures the actual amount of moisture in the air, which is why meteorologists use it to describe how the weather feels.
How accurate is the Magnus dew point formula?
The Magnus-Tetens approximation used by this calculator is accurate to within about 0.35 °C for temperatures from −40 °C to +50 °C and relative humidity above 5%. For most weather, HVAC, and industrial applications this is well within acceptable tolerance. Laboratory-grade applications may require a psychrometric chart or exact steam-table equations.
Can relative humidity exceed 100%?
In clean air, RH above 100% causes condensation immediately. However, supersaturation up to about 101–102% can briefly exist when there are no condensation nuclei (dust or particles) present, which happens in clouds and in laboratory conditions. Values above 102% from a home sensor usually indicate sensor error.
Why does indoor humidity drop in winter?
Cold outdoor air holds very little moisture — air at −5 °C and 80% RH contains roughly 2.8 g/m³ of water vapor. When that air enters your home and warms to 22 °C, the same moisture equals only about 15% relative humidity. This is why indoor RH often falls below 25% in winter, causing dry skin, static shocks, and cracked wood — a humidifier can restore the 30–50% comfort range.
How do I convert dew point back to relative humidity?
Rearranging the Magnus formula: RH = 100 × exp((a × Td)/(b + Td) − (a × T)/(b + T)), where T is air temperature and Td is dew point. As a rule of thumb, when temperature and dew point are equal, RH is exactly 100% — the closer they are, the higher the humidity.
Related Tools
Dew Point Calculator
Calculate dew point from temperature and relative humidity, or reverse it back to humidity. Includes comfort scale and Magnus formula reference.
PDF Converter
Convert documents to and from PDF format. Transform images and Word files to PDF, merge PDFs, and extract pages as images.
Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Get instant accurate conversions with helpful references.
Time Zone Converter
Convert time between different time zones around the world. World clock with time difference calculation.
Pressure Converter
Convert between Pascal, PSI, Bar, Atmosphere, Torr, and mmHg with precision and helpful references.
Volume Converter
Convert between liters, gallons, cubic meters, fluid ounces and more volume units across metric, imperial, and US systems.