Calculating your descent rate

If you’re flying your aircraft on a roughly 3 degree glideslope, try multiplying your groundspeed by 5 to estimate your descent rate. The result will be an FPM value for descent that you should target.

For example, your ground speed is 90knts. Multiply your ground speed by 5, equaling 450. A 450 FPM descent rate will keep you on glide.