A useful template to calculate the furthest Distance removed from an aerodrome that you may travel and safely return with an adequate fuel reserve remaining. This is especially useful when traveling on large overwater legs on the sim or remote areas without an alternate destination. The formula is as follows;
Endurance in hours (- Fuel reserve) X Groundspeed out to destination X Groundspeed home / ( Out + Home)
Hope this helps!
Note: For sim use only! (Obviously)