How to use
This calculator has been recently updated! I've fixed and rewritten everything for Rex/Hairless/LaPerm genes. It is still not 100% proofed but there are no errors or bugs that I am aware of.
This calculator requires basic knowledge of genetics.
I've done my best to indicate phenotype and genotype in an intuitive way. Phenotype (how the cat looks) comes first in each option, genotype (the actual genes in play) is indicated in parentheses afterwards. Some phenotypes have multiple available options due to different genotypes.
Every trait has the most common/simple option set as the default, so if it isn't a factor you're concerned with, just leave it be.
This version of the calculator was coded entirely from scratch after completing the original. It is, as far as I know, the most comprehensive cat calculator there is. People asked for the chances for each trait to be listed, so I did that. I threw in the different fur types and non-fur traits mostly for fun, and because I was assured someone would use it.
For manx, munchkin, and folded ears, homozygous dominant is not an option because those cats die in the womb and are reabsorbed. This has been taken into account in the calculations, which is why you can have a 66% chance of one of these genes.
I had to research coat types myself and attempt to predict how different genes would interact while keeping it simple. As far as I know wirehair can actually interact with rexed fur in unique ways, so I distilled it down to that and one type of rexed fur at a time.
Traits such as albinism and other rarities were left out for practicality, and some options for the Rex/Hairless trait were left out, but it should be accurate. Errors have been found and the code hasn't been as thoroughly checked as I would like, so keep an eye out and let me know through email or tumblr if something looks odd to you.