You might want to rethink that design
You measure the port and then use simple math to figure it out. But if the box is being built, then you should already know what the volume for your port is.
Box is being built, but not by me. I was asking the question for my own knowledge.
About the same as your comments, no worries its cool. Not everyone is up to the challenge or has the knowledge to make a wedge box sound decent.
Thanks for the help
Box looks fine to me...and OP just your simple L x W x D will tell you port dimensions. If you use an aero port it's pi * d * length. Make sure to divide by 1728 to see what it is in cubic feet