To calculate descent distance, what factor is multiplied by the altitude you need to descend?

To calculate descent distance from altitude, pilots often use the rule of thumb that for every 1,000 feet of altitude, approximately 3 nautical miles (often simplified to 3 miles in some instances) of horizontal distance should be traveled in order to descend safely and efficiently. This is based on an approximation of descent rates that allows for a controlled and safe approach without being too abrupt or steep.

The reasoning behind using this particular factor is that it accounts for a typical descent that balances the need to reach the target altitude with the need for adequate time and distance to prepare for landing. Depending on the speed of the aircraft and the particular approach path, 3 miles per 1,000 feet provides a good framework for pilots to start their descent at the appropriate point, ensuring safety during approach and landing.

In operational terms, using this factor helps pilots to manage their descent profile effectively, thereby facilitating a smoother transition from cruising altitude to final approach.