Countertop Span/sag Calculations [closed]

I came upon enough 3"x3" structural aluminum square tubing to build a countertop over the washer, dryer, and sink. I wanted to double check the sag/deflection of the tubing but am having trouble figuring it out. I think it should be strong enough but just wanted to double check. Where is a simple calculator that I can plug in the components and see if the aluminum will bend. The front piece is 3x3x7.5'- 1/4" thick. There will be 3x3x24" pieces going to the back wall to support as well. Really I'm concerned about the main span. I don't imagine it would get over 300 lbs across the whole weight. Thanks

• Unless you put the washer, dryer and sink Ontop of the shelf I don't think you'll have an issue with sag/fatigue. [no math done since you're not paying] Jan 12 '17 at 21:23
• Since I'm not paying you? Thanks for the input btw. Jan 12 '17 at 21:25
• Is this countertop going to be the standard sort bought from a kitchen showroom, or homemade from a piece of plywood? If bought from a kitchen showroom then it has a lot of stiffness in and of itself; I would think the additional aluminium tube would be fine. I've spanned over 5' with a kitchen countertop just supported at the ends and the back. Jan 13 '17 at 12:06
• I have 3/4 plywood that will go under a 1" piece of granite like stuff. I don't think it's actually granite but it looks like it. Jan 13 '17 at 12:27
• Just to be clear, you have a 7.5" span with no vertical supports? Jan 16 '17 at 3:00