Mythic hit at roll 123,456 with 5x luck after code boost timing.
Updated 2026-05-10 - 10K Monte Carlo trials per query
Slime RNG Odds Simulator: Calculate Cumulative Probability for N Rolls
I built this odds simulator after rolling 100 times to verify the early-rarity math, then realizing the standard luck calculator does not show what most players actually want to know: "if I roll 5,000 times at 20x luck, what is my probability of hitting Mythic?" Below input your scenario and see the cumulative probability + percentile breakdown.
The Slime RNG odds calculator is tuned for N-roll planning. At 10x luck, Mythic over 50K rolls is about 39%, not 99%; the near-99% case is closer to 500K rolls. That correction is exactly why this odds simulator exists.
Calculate My OddsTL;DR
I am Jim Liu, a Sydney indie dev, and I built this Slime RNG odds calculator after a 100-roll verification pass and a 10K Monte Carlo trial workflow. My goal is simple: show cumulative probability, percentile rolls, and time estimates for the exact Slime RNG scenario you are about to play.
How the Odds Simulator Works
The Slime RNG odds calculator starts with the target rarity denominator, converts it into a base per-roll chance, multiplies that chance by your luck multiplier, then keeps the result below certainty. The formula is plain enough to audit: if Mythic is modeled as 1 in 1,000,000 and your setup is 20x luck, the effective per-roll probability is 20 / 1,000,000.
I separate this page from the first-hit time calculator because players often ask a different question. They do not only want to know the median time. They want to know whether 1,000, 5,000, 50,000, or 200,000 attempts gives a meaningful cumulative probability before they commit a boost window.
Calculate Cumulative Probability for N Rolls
Computing 10K trials...
Percentile Breakdown: 10% / 50% / 95% Confidence
The percentile table tells you how many rolls are needed for 10%, 25%, 50%, 75%, and 95% confidence. A 50% row is not a guarantee; it is the point where half of comparable attempts have hit. The 95% row is the stress test I use before spending GIVEMELUCKNOW or stacking Huge Lucky utility.
The Slime RNG odds calculator also turns each percentile into time using your roll speed. This matters because a slow public server and a clean private-server rhythm can produce very different real play sessions even when the luck multiplier is identical.
Common Scenarios (Mythic / Inverted / Huge)
Tap a preset to load the widget, run the monte carlo simulation, and compare the exact cumulative probability. These are planning cases, not promises.
Why Cumulative Math Matters (vs single-roll odds)
Single-roll odds are useful for labels, but cumulative probability is the planning number. A 1 in 1,000,000 Mythic still has a meaningful chance if you combine enough attempts with luck. The same logic also shows why a 50x Inverted chase can still miss after 200K rolls without being suspicious.
This Slime RNG odds calculator deliberately shows the uncomfortable miss cases. I do not want my own guide to make players feel "due" after a long miss. Roblox RNG does not owe the next roll a hit unless the game exposes a pity mechanic, and Slime RNG has not exposed one for these tiers.
Methodology - Verifying the Formula
How I built this odds simulator: cumulative probability = 1 - (1 - p)^N, where p = base_rate * luck. The monte carlo simulation then samples 10,000 first-hit runs using the same effective probability, sorts the results, and draws a log-scale histogram.
On May 8 I cross-checked 100 rolls at 5x luck against the Common tier. The expected hit count was about 50, and my manual run got 47 hits, which sits inside normal statistical spread. I also rolled longer sessions while building this site and use those logs to catch obvious formula drift.
Limits: the model assumes uniform RNG, ignores back-to-back cooldown artifacts, and treats luck as a direct multiplier. Community-reported actual rolls can expose batching artifacts that a clean formula misses, so I keep formula output and field reports beside each other.
Source checks I use: Roblox Creator documentation for platform behavior, Stouts Studio community announcement flow for Slime RNG codes and rates, and cross-game formula baselines from Pet Sim 99 odds calculator discussions. The Slime RNG odds calculator does not claim private Stouts Studio data.
Community-Reported Results
Legendary hit inside 8,400 rolls at 12x luck while farming a rebirth rebuild.
Huge Lucky reported around 410,000 rolls with mixed permanent luck and speed upgrades.
Inverted missed through 200,000 rolls at 50x luck, which still fits the cumulative probability curve.
Mythic missed after 40,000 rolls at 10x luck, then hit near 71,000 rolls on the same boost plan.
Rare and Epic outcomes matched the table closely during a short 100-roll manual verification run.
Submit your result with target rarity, luck multiplier, roll speed, roll count, and whether a code boost was active.
Why this matters
Community-reported actual rolls are not cleaner than the formula, but they can reveal whether real Roblox sessions have batching artifacts, lag gaps, or boost timing mistakes. I use them as a reality check, then keep the Slime RNG odds calculator formula visible so the page stays auditable.
FAQ
Is this Slime RNG odds calculator the same as the luck calculator?
No. The luck calculator focuses on first-hit time. This Slime RNG odds calculator focuses on cumulative probability after a fixed number of rolls.
What formula does the odds simulator use?
It uses cumulative probability = 1 - (1 - p)^N, where p is base rate times luck and N is your roll count.
Why run 10K Monte Carlo trials if the formula is exact?
The exact formula answers the N-roll probability. The 10K Monte Carlo simulation shows the spread of first-hit outcomes so players can see the unlucky tail.
Does the tool read my Roblox account?
No. The odds simulator is browser-side JavaScript. It does not read your account, inventory, or private roll history.