How much Umbrella do I need?

[Mary M.]

What is the appropriate amount of Umbrella coverage does one need to ensure adequate/robust (but not excessive) coverage? 

To put some (fictitious)numbers out :

Prop 1 valued at 1million 

Prop 2 valued at 2 million 

Addtl assets valued at 750K

Assuming normal GL coverage, how much umbrella do I need?   Do I add up my coverage and subtract from the value of my assets? then what is left over is umbrella?? so confused! lol!~