First time build question

[Misconduct]

Hello All

I’m a first time builder and need some help please.
I’ve fabricated a firebox and smoker ready for welding but after reading several posts I am still a little confused
I need to cut an opening in my firebox and smoker to attach the pieces together and need some advise on opening size.

The dimensions of both are as follows

Firebox 16” sq
Smoker chamber 16”w x 16”d x 48”h

Can someone please provide the opening size. Of note I plan on having 2/3 of firebox below bottom of smoker?
I have provided pictures for visual effects nothing has been welded as of yet

Thank you all , big fan of the site and can’t wait to start trying the smoker

 

[Brokenhandle]

Standard Reverse Flow Smoker Calculator... by DaveOmak and others... Ready to use.. rev5.. 6/19/15.

Here's to "Alien BBQ" and the folks that first put the calculator together and "1728 Software Systems" for this great "Circle Calculator" and all the folks at "SmokingMeatForums", with a special shout out to Ribwizzard, that contributed their ideas and feedback while this thing was coming...

www.smokingmeatforums.com

Check that out, see it it helps.
Welcome to the forum. If you haven't already stop over in Roll Call and introduce yourself.

Ryan