Mutation Odds Calculator: How Rare Is That Roll?

How the odds calculator works

Pick the mutation you’re hunting from the dropdown — it’s grouped by tier, so SS-tier jackpots like Secret and Void sit at the top and common C-tier rolls like Pure and Moonlit sit near the bottom. Type in how many unboxes you plan to open, and if you’re chasing a weather-gated mutation (Moonlit, Firefly, Wet or Shocked), flip the weather toggle to see how an active event changes the math. The result panel updates instantly: the headline number is your chance of landing at least one of that mutation across the whole run, the expected count shows how many you’d statistically pull on average, and the breakdown lists exactly how many unboxes you would need for a coin-flip (50%) or a near-lock (90%) shot.

Estimated odds for all 22 mutations

The full comparison table under the calculator ranks every mutation (Rainbow excluded — its multiplier is still unconfirmed) from most common to rarest, with its multiplier, how you get it, and the rolls needed for a 50% and 90% chance. Tap any row to load that mutation straight into the calculator above. Reading it top to bottom is basically a rarity curve: Dirty at the top needs only a handful of unboxes for a 90% shot, while Secret at the bottom can take several hundred.

Where these odds come from — and where they don’t

We want to be upfront about the limits here. Storage Hunters’ developer has never published a drop-rate table, and we have not datamined the game’s server code — nobody outside the dev team has. What we do have is a strong, consistently reported pattern: low-multiplier mutations like Dirty and Cobwebbed show up constantly in normal play, while Void and Secret are rare enough that most players go dozens of hours without seeing one. The calculator turns that pattern into numbers by weighting each mutation’s estimated chance inversely to its multiplier, then normalizing the 22 confirmed-multiplier mutations to sum to 100%. It is a model built from the one relationship everyone agrees on, not a leak — every panel on this page says “estimated” for exactly that reason.

Is grinding for a rare mutation actually worth it?

Run the math before you commit hours to it. At our modeled odds, a 50% shot at Gold (4x) takes roughly 21 unboxes — a normal afternoon session, and even Diamond (8x) is only around 41. A 50% shot at Void (35x) jumps to roughly 180 unboxes, and Secret (50x) sits north of 250. That is not a small difference: chasing Void or Secret specifically is a multi-session grind, and it only pays off if you land the mutation on an item worth grinding for in the first place. A Secret on a $200 Junk Yard trinket is $10,000 — good, but not life-changing. A Secret on an $80,000 Shipyard haul is $4,000,000, which is the entire reason people chase it. Before you sink hours into hunting a specific high-tier mutation, check what your current best items are worth on the value calculator — if nothing you own clears a few thousand in base value, the expected payoff usually doesn’t justify the grind yet.

Weather boosts, and why they’re estimated too

Four mutations are weather-gated rather than pure random rolls: Moonlit and Firefly ride Moonlit events, Wet and Shocked ride Rain. Players consistently report seeing more of these during their linked weather, which is why the calculator lets you toggle a boost for them specifically. We use +60% as our estimate — enough to reflect a real, noticeable lift without pretending we know the developer’s exact number. If you’re farming Firefly, the practical takeaway is the same either way: open containers during Moonlit, not after it ends. Full drop mechanics for each weather-linked mutation are on the mutations guide, including which weather triggers which roll.