THIS IS THE OLD FILE.
This is a program that calculates probability, and comes pre-programmed with data relevant to the answer. To access this calculator, press "Clone or Download," then "Download as ZIP." Then, unzip the folder, and open the Chance-Calculator.html file included. It will open in your browser, but may not work for all browsers. It will work in Chrome and Internet Explorer. I'm not sure about any others.
This is a former shinychance calculator I programmed a little while ago, but have adapted to handle similar calculations. Pretty much, it takes a percentage or fraction value for the likelyhood of something happening (like a 1/4096 chance to encounter a shiny) and a number of attempts, then calculates the chance of said circumstance happening once for the given number of attempts. For example, if you try to find, say, a female pidgey, and encounter 2 pidgeys, there is a 75% chance of one of them being female.
This calculator can find all sorts of stuff like that. I may end up using this occasionally to support answers on PKDB, so I've optimized it to be as flexible as possible.