What is your favorite Rule of Thumb?

Found this little gem for calculating rate of climb necessary to satisfy a particular climb gradient (here)


Let's say you know your ground speed, and assume a "standard climb gradient" of 200ft per nm.  Take your GS and divide by 60, multiply the result by your climb gradient, and the answer is your minimum rate of climb in feet per minute.  Easy Peasy Lemon Squeezy!

A real world example:  90kts groundspeed, 200 ft/nm required gradient gives us:

90/60 = 1.5  * 200  =  300 fpm min ROC

makes sense that the faster guys in the TBM's and Meridian's need a steeper ROC

180/60 = 3  * 200 = 600 fpm min ROC


What is your favorite rule of thumb?