1x1 square tubing

I'm making a new bed floor and wondering what thickness 1"x1" square tubing I should use? Should I go with 16 or 18 gauge sheet metal?

My entire floor structure in my blazer is just 1/2"x1/2" 16 gauge tube. 1x1 the max I'd use is 1/8 but even that is probably overkill.
I'd say 16 gauge for the sheet.

your floor looks pretty damm good. I don't wanna have to run too much tubing and I don't want problems making bed mounting spots on the tubing either.

GO 3/4" TUBING THAT SHOULD BE FINE. THAT AND IT IS A LITTLE TALLER TO HELP WITH MOUNTS.
I WOULD GO WITH 16GA. TO UNLESS YOU WANT TO DO A LOT OF SEEM WELDING. 16GA COME IN BIGGER SHEET SO YOU CAN 1 PIECE THINGS

I'd use 16 gauge tube.