A simple trade-skill add-on for TBC Classic which displays the percentage chance of a skill-up beside your craftable items list in your trade-skill window (See images for example). This add-on was created for TBC Classic, and has not been tested on WoW Classic, although it may still work.
The calculations are based off of the following formula from the game's wiki. Contrary to what many think, the chances are not as simple as green, yellow and orange being 25%, 75% and 100% respectively. This add-on simply shows you the true probability of gaining a skill-up when crafting an item, displaying them beside each item's name in your trade-skill window. Gray items don't display anything at all, since they are always 0%. In other words, you can now see why you crafted 30 green items in a row and still didn't hit a skill-up :P.
Any bug reports or suggestions are welcome and can be reported here or on the github repository in the 'issues' section.