I came up with this the other day and posted it on SMD, I figured I should post it here too.  Hopefully someone will find it useful. I'm sure most people here have come across the "12-16 sq in of port area per cube" guideline for slot ports and the "9-12 sq in per cube" for aeros.  The problem with both of these is they only consider box volume.  Both input power and tuning frequency, along with box volume, have a great effect on how much port area you need.  This is why I've been recommending to people to NOT use those rules of thumb.  Online you can find several websites (such as carstereo.com) that have port area calculators using the formulas developed by Dickason or Small.  These have a similar problem of ignoring input power and these formulas aren't really relevant for our modern, high Xmax subs.  The best solution is to use box simulation software (WinISD, BassBoxPro, etc) to determine how much port area you need based on the specifics of your system.  However this is time consuming and not everyone has access to that software or has the desire to learn how to use it well.  I wanted to come up with something is quick and easy to use, and should hopefully give a lot better results than the rules of thumb or the obsolete formulas.  Here it is, to make this easy I'm using Google Docs: https://docs.google.com/spreadsheets/d/1VREceNxz9YOcFlI8O_TG62-4O-l3Q2IjD5qsEkVVh28/edit?usp=sharing This is what it looks like: This will probably always be a work in progress, but so far I think it should work pretty well.  I encourage everyone to use it and give me your feedback!  Please note that due to the fact its a Google docs document multiple people can edit it at the same time.  So if the numbers are changing on you while you use it, its someone else, just have patience.