Calculate when to begin descent using altitude to lose, groundspeed, and descent rate. This free aviation calculator helps pilots plan smoother descents and estimate top of descent distance.
Use either method below. The first method calculates descent distance from vertical speed and groundspeed. The second method uses the common 3 to 1 rule for quick planning.
Top of descent is the point where a pilot should begin descending in order to reach a desired altitude at the right time and distance from the destination or fix.
Proper descent planning helps create a stable arrival, reduces workload, and makes it easier to meet altitude restrictions and traffic pattern entry goals.
It is a quick planning shortcut that uses about 3 nautical miles of descent distance for every 1,000 feet of altitude to lose.
Higher groundspeed means you cover more distance during the same descent time, so you need to start down earlier.
Yes. Your target altitude should be the altitude you actually want to reach, whether that is traffic pattern altitude, an approach altitude, or field elevation plus a specific margin.
No. It is a useful rule of thumb for planning, but real descent planning depends on speed, wind, configuration, and operational requirements.