Comment That's a smidge under 4" for the entire state (Score 2) 330
The area of the state of California is 163,696 square miles.
$ units --verbose
Currency exchange rates from www.timegenie.com on 2014-04-02
2866 units, 109 prefixes, 79 nonlinear units
You have: 11 trillion gallons
You want: 163696 in mile^2
11 trillion gallons = 3.8666624 * 163696 in mile^2
11 trillion gallons = (1 / 0.25862097) * 163696 in mile^2
I find '4" over the entire state" to be a little bit more manageable than some unscaled number with a bunch of zeros, but maybe it's just me.