I believe you are referring to the fraction of freshwater that is vapor.
As per United States Geological Survey (USGS), only about 0.001% of our freshwater supplies on planet Earth are present in the atmosphere as (mainly) vapors and clouds. Even though almost 71% of Earth's area is covered with water, 96.54% water is present in oceans and seas. In fact, only about 2.5% of the total water is freshwater and even out of this small fraction, 98.8% is located in ice caps or as underground water.
Since we are very much dependent on lakes and rivers as our chief water supply source, it is interesting to note that only 0.007% of total water on Earth is available as freshwater in the lakes. River contain even less freshwater and the corresponding percentage is 0.0002%.
To put things in perspective, oceans/seas/bays contain 1.34 billion cubic kilometers or water, whereas the atmosphere (mostly as vapors) contain 12,900 cubic kilometers of water.