How much gas left when "low fuel" light goes on....?

Quick question just out of curiousity..... I have a 2001 Suburban and we rarely let it get below 1/4 tank. We live about 8 miles from town and want to know ( ballpark figure ) how much gas do you usually have left when the "low fuel" light goes on ?? I don't need the lecture about not running it low, we don't ( it is bad for the fuel filter...blah blah blah) ....just curious.