How do you calculate relative humidity?

How do you calculate relative humidity from actual humidity?

• Answer:

  actuall humidity is given as the amount of water. use a table stating how much water the air can hold at the given temp, this is your 100% humidity. now calculate howw much you got and that would be relative humidity Answer: To calculate relative humidity you need a wet bulb and a dry bulb thermometer and a psychrometric chart (a graph of the physical properties of moist air at a constant pressure). The chart graphically expresses how various properties relate to each other. Using an ordinary thermometer you read the dry bulb temperature(DBT). You will locate this temperature on the x-axis of the chart. Next you will determine the wet bulb temperature (WBT) from a thermometer who's bulb is covered with a wet wad of cotton and typically waved in the air until the temperature goes to its minimum. This works because dry air evaporates water and evaporation cools the wad. The temperature it reaches is related to the air's humidity. This value goes on the curved line at the top of the chart. The relative humidity (RH) is read off the chart from the intersection of the lines from these two points.