Round to square port calculators?

Anyone know where I can locate a calculator that would give me specs on taking numbers for a round port to change them over to a square/rectangular port???

Thanks in advance!!!

If that's all you need to do you just figure the area of a circle using piRsquared (3.14 X radius of circle squared).  That gives you the total square inches of opening.  Then you decide on a length of the slot opening you want to use and divide that length into the total sq inches to get the other dimension of the slotted port.

Here's an example:  I have instructions for a port 4" round and 12" in length.  Conversion would be:

The diameter of the port is 4" so the radius is half of that - 2".

2 squared (2 X 2) = 4

3.14 (pi) X 4 = 12.6"

I want the long length of my slot to be 10", so

12.6 / 10 = 1.26".  The slot will be 1 1/4" X 10" and the length of the port will remain the same at 12" long.

The slot opening dimensions can be any two numbers that multiply to make the total square inches that the round port is.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

It's okay...I was able to find what I needed here...

http://www.carstereo.com/help/Articles.cfm?id=31