What is the formula to calculate cloud base?

The formula for calculating cloud base is derived from the relationship between temperature, dew point, and altitude. The correct formula, Temperature - dew point / 3 x 1000, effectively estimates the height of the cloud base in feet above ground level.

In the formula, the difference between the temperature and the dew point reflects the amount of moisture in the air. A smaller difference indicates that the air is more saturated, which typically means that clouds will form at a lower altitude. Dividing this difference by three allows for a conversion that takes into account the rate at which humidity affects altitude; specifically, it approximates that for every 3°C difference in temperature and dew point, the cloud base rises by about 1000 feet.

Using this formula is crucial for pilots as it allows them to anticipate cloud heights, thereby aiding in flight planning and safety by ensuring that they can maintain visual flight rules (VFR) if necessary.