Gacha Probability Calculator
Enter a per-pull drop rate and the number of pulls to see your real chance of landing at least one rare item — and why it climbs fast but never hits 100%.
Your true odds over many pulls
A 0.6% rate sounds tiny, but over 90 pulls the chance of at least one rare is about 41.8% — this tool shows that combined probability instantly.
Independent pulls only
The formula assumes every pull is independent with the same rate. It does not model pity or soft-pity systems that guarantee a drop after a counter.
What does this calculator tell you?
The chance of at least one rare item
The gacha probability calculator turns a per-pull drop rate and a number of pulls into the single number players actually care about: the chance of getting at least one rare item across the whole run. A banner might advertise a 0.6% rate per pull, which feels hopeless on its own, yet over dozens of pulls the combined odds grow much larger. This tool computes that combined probability with the formula 1 − (1 − p)ⁿ, so you can plan how many pulls you need before a rare drop becomes likely.
Enter the per-pull drop rate as a percentage and the number of pulls to get the chance of at least one rare item right away.
The trick is to work out the chance of missing every single time and subtract it from one. If a single pull has probability p of success, then 1 − p is the chance it fails. Across n independent pulls the chance of failing every time is (1 − p)ⁿ, so the chance of at least one success is one minus that.
P(at least one) = 1 − (1 − p)ⁿHere p is the per-pull drop rate written as a fraction — a 0.6% rate is p = 0.006 — and n is the number of pulls. The result is a probability between 0 and 1, which the calculator also shows as a percentage.
Suppose a banner has a 0.6% chance per pull and you plan to make 90 pulls.
Convert the rate to a fraction
0.6% becomes p = 0.006, so the chance of missing one pull is 1 − 0.006 = 0.994.
Raise the miss chance to the power of n
0.994 to the power of 90 is about 0.5818 — the chance of missing on every one of the 90 pulls.
Subtract from one
1 − 0.5818 ≈ 0.4182, so the chance of at least one rare item is about 41.8%.
The headline number answers a different question from the per-pull rate. A 0.6% rate per pull does not mean you have a 0.6% chance over many pulls — it means each individual pull has those odds, and the combined chance of at least one success is far higher. Over 90 pulls that 0.6% rate becomes roughly 41.8%, and the curve keeps climbing the more pulls you add: it doubles the per-pull rate quickly at first, then bends toward 100% without ever reaching it. That last point matters. Because (1 − p)ⁿ is always greater than zero for any finite number of pulls, the probability of at least one rare item gets closer and closer to certainty but never becomes guaranteed. Even 300 pulls at 0.6% leaves a small chance of walking away empty-handed, which is exactly why the math can feel so cruel — and why doubling your pulls does not double your already-high odds once you are well past the halfway mark.
The formula is exact for the model it describes, but real gacha systems add rules it does not capture.
Independent pulls, a fixed rate, and no pity
This calculator assumes every pull is independent and shares the same drop rate, with no memory of previous pulls. Many real games layer on pity or soft-pity systems that raise the rate or guarantee a rare item after a set number of misses, and some banners use rate-up or split rates for featured items. Those mechanics make your true odds higher than the plain 1 − (1 − p)ⁿ result once you approach the pity threshold, so treat this number as the baseline before any guarantee kicks in.