The Comprehensive Fishing Guide/Calculator
Link to Google Sheet: Fishing Guide/Calculator
(Note that the copy provided does work without you needing to make another copy but it would be best to make your own copy.)
This is a fishing guide I have been working on, it started out as just a way to calculate the chances for each tier of rarity, which was pretty simple to do, but I have now expanded it to detail the requirements for catching every item and to give the chance for specific items. The list of possible fishing catches goes over every single fishable item and its requirements, and outlines the specifics of how certain items or biomes take priority over others. The list is very helpful for determining if you can catch certain items at specific locations or elevations, and for keeping track of the biome priorities the game uses.
Contents of the Guide
Sheet 1: Tier Calculator
This is the simplest of the 3 sheets, all it does is take a given fishing power and calculates the chances for each tier of fishing catch. There are five different rarity tiers, along with the possibility of no tier at all, and the additional Crate roll. Calculating the chances for a specific tier is fairly simple to do, the wiki has the formulas and the math is simple, the interesting part is determining all the different hybrid tiers. In total there are 31 hybrid tiers, and also no tier at all, and we can use these hybrid tiers to calculate the exact chances of catching a certain item, as explained in Sheet 3.
Sheet 2: Detailed list of possible catches
Sheet 2 does not contain any formulas, it is merely a collection of information relevant to fishing. All possible fishing catches are given, including Blood Moon enemies and Duke Fishron, with the applicable tiers and any additional requirements. It covers pretty much everything there is to know about fishing, detailing chances for Blood Moon enemies, biome priorities, size of the fishing pool, and what makes Lava and Honey fishing so slow.
Sheet 3: Fishing Calculator
This sheet took far longer than the others to put together, I was able to put together chances for crates, lava fishing, and honey fishing by more or less brute-forcing the math, and attempted to brute-force the items for fishing in water before realizing how hopeless it was. Eventually I found a way to use the 31 hybrid tiers to calculate chances for specific items, using the specific priorities the game gives to certain enemies/biomes. Since I did switch methods partway through, the sheet is a bit inconsistent in the way it displays information between regular items caught in water and everything else. The sheet still should be accurate though, if you notice something not working as it should let me know and I'll try to fix it. I also did make some assumptions for the sake of simplicity, no junk chances are calculated, and no quest fish are calculated either. I may make a better version at some point using the hybrid rolls to find the chances for every item, including junk and specific quest fish.
Sheet 4: Angler rewards
Shows you chances for all the angler rewards based on how many quests you have completed and how happy the Angler is. I know the chances are changing once 1.4.4 comes out, but figured I would go ahead and make it now anyway. The chances are pretty interesting, really shows how rare the decorative items get once you get past 150 quests. What is interesting is that making the game think you still want at least one fishing accessory and at least one Fish Finder component drastically increases the chances of getting a decorative item, since it now only rolls twice instead of six times total.
How the Calculator works
The 31 hybrid tiers are calculated using the given fishing power, and then added together for a total chance. Instead of trying to calculate the chances to catch an item it calculates the chances to not catch an item. For example, the Frog Leg is the second non-crate item checked, with a 1 in 5 chance of being caught if the Legendary roll succeeds. Using the hybrid tiers, every tier that does not have a successful Legendary roll can be ignored, it will be the same value it was before. The tiers that have a successful Legendary roll though will be multiplied by 4/5 since 1/5 of the time that tier will result in a successful Frog Leg catch. The totals from the previous row and the current row are then checked to find the difference between them. One particularly troublesome part was trying to accurately replicate how the game calculates chances when in both Crimson and Corruption biomes. If you are in both evil biomes at the same time there is a 50/50 chance for a fishing catch to use either the Crimson loot table or the Corruption loot table. This means that one catch can potentially either be a Crimson Tigerfish or a Hemopiranha, but never a Crimson Tigerfish or Ebonkoi. To accurately replicate this I had to make two more copies of the hybrid rolls, each one taking half the value of the original, and then using one to calculate chances for Corruption loot while in both biomes and the other for Crimson loot while in both biomes. After calculating both evil biomes fishing loot the two copies are added back together.
