please convert to inches for me?

12volt.com

no way u running a 25" long port in a .75 cu foot box. impossible. redo your calculations, something is wrong, you shoud NOT need a port that wide and long in a box that small. use the calculators in teh wbesite above. I'm 95% sure your specs are off

pss- let me also add that I'm curious as to what you are trying to tune the box to. what are the manufacturer recommended specs for tuning in sealed versus ported. usually ported is at 35-42hz

Obviously ricardo has never built, or even thought much about a ported box - the 25" port would require a bend, maybe 2. Not really a big deal.

The volume of the port is .18 cubic feet so you'd add that to your .8 making the gross volume .98cf (I'd just call it 1.0)

1.0cf = 1728 cubic inches so your ported section, obviously, is 1728 and the sealed is 1296

How you want to build it is up to you. The ported chamber could be 12x12x12

That would make your sealed portion 12x12x9.

Just take

LxWxH = 1728

and LxWxH -1296

plug in numbers you like for 2 of the 3 and solve for the other.