Humidity Calculator
Humidity describes the proportion of water vapor in the air, liquid water (e.g. rain, dew) does not count. The relative humidity indicates the proportion of the highest possible saturation. 100% means that no more water vapor in the air can be absorbed. The absolute humidity indicates the mass of water vapor per cubic meter of air. The higher the temperature, the more water vapor the air can hold.
This calculator uses an approximate formula1 that is accurate to within 0.1% at temperatures between -30°C and 35°C and normal atmospheric pressure. The more the temperature deviates from this range, the more inaccurate the result becomes.
This result applies to the theoretical case that the room is hermetically sealed and the water completely dissolves in the air. In practice, more water than the calculated amount will be necessary. On the other hand, most rooms are not empty, which reduces the space for air and correspondingly reduces the amount of water required. An example of a sealed space where humidity should be controlled is a terrarium.
Physics commonly uses SI units. Here is a calculator to convert lengths, temperature, pressure, speed and other units.