Why I Built Another Spreadsheet for This
I spent two generations doing this manually. The first was Gen 3, when I had a notebook and a calculator and zero understanding of what was actually happening behind the scenes. By Gen 8, I had a dozen Excel tabs with different formulas trying to approximate cumulative probability, none of them quite right. This is what happened when I just decided to fix it properly. This is a straightforward tool. You input the current shiny rate for the game you're playing, the number of Pokemon you've already encountered, and whether you have any modifiers active like the Shiny Charm or Masuda Method. It outputs your cumulative probability of finding at least one shiny by that point, and it projects how many more encounters you'd need to reach a target probability like 50% or 90%. Nothing fancy. It does the math so you stop second-guessing whether your streak is cursed. The base shiny rates vary by generation, which matters more than most people realize. Gen 3 and 4 stuck with the classic 1 in 8192. Gen 5 introduced the chain mechanics for wild encounters in some games, but the base rate stayed the same unless you were breeding. Gen 6 and onward settled into a general baseline of 1 in 4096 across most main series titles. Scarlet and Violet made this consistent, which actually made planning easier because I no longer had to look up whether a specific game was using the older rate or the newer one.
The modifiers stack multiplicatively, not additively, and this is where everyone gets it wrong. The Shiny Charm gives you two extra rerolls per encounter in modern games. That means instead of 1 in 4096, you get 3 chances out of 4096, which is approximately 1 in 1365. It feels like it should be triple the odds but mathematically it's not quite that clean. The Masuda Method adds another four extra rerolls when you're breeding two Pokemon from different language games, bringing it to 7 total rolls or roughly 1 in 585 with the Charm already applied. Put all three together in Scarlet and Violet and you're looking at 9 rolls out of 4096, which works out to about 1 in 455. That's the actual number, not 1 in 1365 times 1 in 585 or whatever someone will tell you on Reddit. I ran into a real edge case in Pokemon Legends Arceus that broke every planner I could find online. That game uses a completely different encounter system where shiny rate depends on silph sashes and research task completion, not the standard chain or breeding mechanics. The base rate there for a fully completed dex entry with the max silph sash is 1 in 128, which is dramatically higher than anything else. A standard planner would treat it as 1 in 4096 and give you wildly misleading projections. I had to hardcode a separate calculation path for Legends Arceus with its own rate table, and even then I had to verify it against community-discovered values because the game never officially published the exact numbers. If you're hunting in that game, use a custom rate input rather than trusting the default setting.
How to Use It Without Wasting Time
The core workflow is simple enough that most people overcomplicate it. Open the planner, select your game or enter a custom rate, type in how many encounters or eggs you've done, and hit calculate. The output shows your current cumulative probability and a projection table for common milestones. I usually keep it open alongside my game on a second monitor so I can log encounters as I go without switching windows. For mass outbreak hunting in Scarlet and Violet, the effective rate changes as you defeat more Pokemon in the outbreak. After clearing 30 outbreaks, the base rate shifts. After 60, it shifts again. The planner has a section for this where you input your outbreak progress and it adjusts the per-encounter rate accordingly. This alone cut my verification time down from rough estimates to about 15 minutes per target, which sounds minor but adds up when you're hunting the same Pokemon across multiple outbreaks. Breeding is where the planner becomes genuinely useful rather than just convenient. People tend to lose track of how many eggs they've actually hatched across multiple sessions. I've lost count of how many times I started a new breeding run thinking I was behind when I'd already done over 200 eggs. The planner tracks this if you log each session. You enter the number of eggs for that sitting, and it updates the running total with the correct cumulative probability. Doing this accurately is what separates someone who plans their hunt from someone who just hopes.
Get the Full Details
There's a known limitation with the cumulative probability formula that trips people up. The planner uses the standard complementary probability approach: one minus one minus the rate raised to the power of encounters. This is mathematically correct but it hits floating point precision issues at very high encounter counts. Once you go past roughly 10,000 encounters, the calculator starts reporting probabilities that are off by tiny fractions. For practical purposes this doesn't matter since you'd have found your shiny long before then, but if you're doing bulk calculations for an spreadsheet project or something similar, use a library that supports arbitrary precision arithmetic instead of relying on standard double precision floats.
Download and Setup
The planner is distributed as a Google Sheets file so you can copy it to your own drive and modify it without touching the original. The download link is in the resources section of the thread. There's also a standalone Python script for people who prefer command-line tools and want to batch process encounter logs from save data exports. Both use the same calculation engine so results will match. Setup takes about two minutes. Download the sheet, make a copy, and you're ready. The sheet has three tabs: one for wild encounters, one for breeding, and one for custom calculations where you can input any rate and any encounter count. The wild encounter tab auto-populates with standard rates for each main series game from Gen 3 through Scarlet and Violet. If your game isn't listed, switch to the custom tab and type in the rate yourself. I keep a reference sheet open when I'm not sure about a game's rate, but most of the commonly played ones are covered. I should mention what this planner doesn't do because people always ask. It doesn't predict when you'll find a shiny. No tool does that and any claim otherwise is just noise. It also doesn't track individual Pokemon stats, IVs, or natures. If you want a full breeding tracker with those features, you need a different tool. This is strictly for probability calculation and session logging. Keeping it focused on one thing is why it works. Trying to make it do everything usually means it does nothing well.
