Relative Humidity Calculator 2026
Calculate relative humidity instantly from temperature and dew point. Find absolute humidity, vapor pressure, and comfort levels for any environment.
Temperature & Dew Point
Enter the current temperature and dew point to calculate relative humidity
The current air temperature.
The temperature at which air becomes saturated with water vapor.
Humidity Results
Relative humidity, absolute humidity, and vapor pressure
Enter the actual temperature and dew point above, then click Calculate Relative Humidity to see the results.
Dew Point Reference Chart
Dew point temperatures (in °C) for common actual temperatures and relative humidity levels. This helps visualize how close the air is to saturation.
| Actual Temp (°C) | Dew Point at 30% RH | Dew Point at 50% RH | Dew Point at 70% RH | Dew Point at 90% RH |
|---|---|---|---|---|
| 0 °C | -15.4 °C | -9.1 °C | -4.8 °C | -1.5 °C |
| 10 °C | -6.8 °C | -0.1 °C | 4.8 °C | 8.4 °C |
| 20 °C | 1.9 °C | 9.3 °C | 14.4 °C | 18.3 °C |
| 30 °C | 10.6 °C | 18.5 °C | 23.9 °C | 28.1 °C |
| 40 °C | 19.5 °C | 27.5 °C | 33.3 °C | 37.9 °C |
Relative Humidity FAQ
Everything you need to understand relative humidity, from basic definitions to how it affects your indoor environment.
Relative humidity (RH) is the ratio of the current amount of water vapor in the air (actual vapor pressure) to the maximum amount of water vapor the air can hold at that temperature (saturation vapor pressure), expressed as a percentage.
Relative humidity is calculated by finding the actual vapor pressure (using the dew point temperature) and dividing it by the saturation vapor pressure (using the actual air temperature). The Magnus formula is commonly used to calculate these vapor pressures accurately.
A comfortable relative humidity level for indoor environments is generally between 30% and 60%. Levels below 30% can cause dry skin and respiratory irritation, while levels above 60% can feel muggy and promote mold growth and dust mites.
Relative humidity is a percentage that changes with temperature, whereas absolute humidity is the actual mass of water vapor present in a given volume of air (usually measured in grams per cubic meter, g/m³), regardless of the air temperature.
As temperature increases, the air’s capacity to hold water vapor increases. If the actual amount of water vapor remains constant, an increase in temperature will cause the relative humidity to drop, and a decrease in temperature will cause the relative humidity to rise.